OS X 10.8.3: Fusion Possibilities For NonFusion Equipped Mac

We’ve been waiting and waiting for Apple to release the next version of OS X Mountain Lion in hopes that the next full version would have all the necessary components to setup a Fusion drive on any Mac capable of installing a hard drive and SSD together. A little over a week ago, Apple released OS X version 10.8.3 and, with one small caveat, our hopes were fulfilled.

The Profusion Of Fusion Confusion

But before we get to showing you exactly how to setup your own DIY Fusion drive, I’d like to dispel some mis-information that has been floating around the web. Up until now, most of the reports you’ve read about creating your own DIY Fusion drive on a machine have been incomplete. There have been many tutorials on how to create a Core Storage volume that have been labeled as “how to create a Fusion drive”. They are two similar, yet different drive configurations. I’ve addressed a lot of this information in comments on the OWC Blog, but figure it would be a good idea to review and further explain what a Fusion drive actually is as opposed to a Core Storage volume.

When Apple introduced Lion, they added a logical volume manager (Core Storage) to the OS. The key factor to Core Storage is that it allows a single volume to span multiple physical disks. Which makes the Fusion drive possible, but it isn’t the only aspect.

What turns a Core Storage drive into a Fusion drive is the introduction of automated storage tiering to mix. This has actually been around since 2005 on larger scale networks where the software moves data across different disk types and RAID levels in order to balance space, cost and performance requirements of a server. Prior to the automation software, this type of data manipulation was done manually.

Most of the terminal command setups we’ve seen online are only initiating that Core Storage volume. It needs the software to run the automated storage tiering to make it a true Fusion Drive. Until now, we’ve only seen that software component in the 2012 Mac mini and 2012 iMac models that ship with their specific builds of 10.8.2

You don’t find out that it’s not truly ‘Fusion’ until the SSD portion has been completely filled up. And even then – what’s on the SSD continues to be read at full SSD speed, so it’s only the new data writes (where existing data on SSD is not being replaced) and subsequent reads of that HDD stored data that are slower due to being on the HDD. The way a Core Storage volume works, it really makes people think they’ve created a true Fusion drive. So, now that you know the difference, the question on everyone’s mind is…

How Do I Create A True DIY Fusion Drive?

Items Needed:

  • A Mac that you can install both a Solid State Drive and a Hard Disk Drive into. So that’s the iMac (2009 or newer), MacBook (Late 2008 Aluminum, or Early 2009 or newer) with Data Doubler, or MacBook Pro (Late 2008 or newer) again with Data Doubler, Mac mini (Early / Late 2009, Mid 2010 Server, and Mid 2011 or newer) with Data Doubler Kit or Data Doubler where applicable, or Mac Pro (Early 2008 or newer).
  • A hard drive and an SSD installed/to install internally – Fusion is designed to work on internal drives only.
  • An external drive to clone to or a Time Machine backup drive – creating a Fusion volume will erase both the SSD and the hard drive, so if you have information on the hard drive you want to keep, you’ll need to have a copy of that data elsewhere.
  • An external hard drive or USB flash drive that is 8GB or larger to boot your  OS X 10.8.3 installer.

Step 1 – Have a copy of your computer’s data.

This process will erase both the installed SSD and hard drive, so if you have data on one or both of these drives, you’ll want to have a copy that’s not on either of the two drives that are going to be part of the Fusion array. If you are installing both a new SSD and a new platter-based drive into, you can put your original drive in an external enclosure, and your data will be there, out of the way. If you’re using the same drive that you already have installed, you will need to copy that drive’s contents to an external one.

Step 2 – Download 10.8.3 from the App Store.

And here’s the caveat I mentioned earlier: At this time, you absolutely need to download OS X 10.8.3 from the Mac App Store. To further clarify, we’re talking about the FULL VERSION – not the update. This is the only way to assure you have the correct version of Disk Utility on your recovery partition. You can do this by going to App Store > Purchases > Click the Download button to the right of OS X Mountain Lion. ***you may need to actually purchase ML if it does not show in the Purchases screen.

Step 3 – Move the Installer to your Desktop.

The Mountain Lion install package will show up in the Applications folder once downloaded. Move it to your desktop.

Step 4 – Right click on the package icon and select Show Package Contents.

Step 5 –  Navigate to Contents > Shared Support.

There you will see InstallESD.dmg. Drag this image file to your desktop.

Step 6 –  Using Disk Utility, restore the InstallESD.dmg file to an External Hard Drive or USB Flash Drive at least 8GB in capacity.

This should be a separate drive other than your clone or Time Machine backup.

Step 7 – Install the new drive(s) in the computer you’re upgrading.

See our video page for our step-by-step instructions on installing one or both drives into your machine.

Step 8 – Boot to the newly created 10.8.3 Installer.

Boot the machine while holding down the Option key at startup and selecting the external hard drive or USB flash drive with the 10.8.3 installer (it’ll have the orange icon).

Step 9 – Open Terminal.

If you installed at least one brand new drive, you will likely get a message about a disk being unreadable. That’s okay; just click “Ignore.”  We’ll be initializing it over the next couple of steps.

You can then open Terminal. You can find it in Applications/Utilities/Terminal.app

Step 10 – Find Your Disk IDs.

In Terminal, type: diskutil list

This will have the command-line version of Disk Utility (diskutil) that lists all the disks attached to your computer. In the results, you will find the disk IDs of the HDD and SSD. Take note of these ID numbers. In most cases (2 drives internally and booted from the external), the IDs will be “disk0” and “disk1.” However, individual results may vary, depending on your setup, so you’ll want to make sure you have the right drives.

Step 11 – Create the Fusion drive array.

In Terminal, type: diskutil cs create drivename driveIDs

This is the command that actually tells your Mac to tie the drives together in a Fusion array.

Broken down, the step does this:

  • diskutil – the command-line version of Disk Utility.
  • cs – this invokes Core Storage, which is necessary for Fusion.
  • create – creates a Core Storage group.
  • drivename – this is the name of the drive and how you want it to appear in Disk Utility (not the Finder – that comes later). You can call it whatever you want; in our example, we named our Fusion array “Fusion.”
  • driveIDs – these are the drive IDs of the drives you want as part of your Fusion array, separated by a space. In our example, they are “disk0” and “disk1”, but it may be different in your setup.

Once you enter in this command, it’ll do its thing and set-up the drives into an array for Fusion.

Step 12 – Get ID information for Fusion array.

In Terminal, type: diskutil cs list

This will give you a listing showing any Core Storage Logical Volume Groups (aka Fusion drive). You will need to do two things here. First, copy the long alphanumeric string for the Logical Volume Group, then note the Free Space for it. You will need both of these for the next step.

Step 13 – Format the Fusion drive so you can put files on it.

In Terminal, type: diskutil cs createVolume groupString jhfs+ volumeName size

This command creates a volume on the Fusion array where you can place your files. Again, since some important stuff is going on here, let’s break down the command.

  • diskutil – again, this is the command-line version of Disk Utility.
  • cs – invokes Core Storage functions, which are necessary for this arrangement.
  • createVolume – this is the command to create the actual storage area for the drive that is represented on your desktop by an icon.
  • groupstring – this is the long alphanumeric string you copied from the previous step. It identifies that the array you created as the one getting a volume placed on it.
  • jhfs+ – the format of the drive. This is Apple Extended Format (journaled), which is recommended for drives with an OS installed on it.
  • volumeName – the actual name of the volume, how it should appear underneath the icon. If there is a space in the name, you should either put the entire name in quotes (“Drive Name”) or put a backward slash before the space (Drive\  Name). In our example, we did the latter, naming our volume “OWC Fusion.”
  • size – this is the size of the volume. In our example, we had a 1.1TB drive. We used “1100g” to denote it as 1100GB (1.1TB in base 10). Alternatively, we could have also used 1.1T, or even 100% as a size.

Once you have this information entered, hit Return and let it do its thing; the Fusion Drive will then be available in the Finder.

Step 14 – Close Terminal and Install OS X.

Now that we have created the CoreStorage volume named Fusion, we can now install the OS and bring over your data.

Close your Terminal window and select the option to Install OS X. Follow the prompts for installation, choosing your new Fusion drive as the destination. You will need an Internet connection to do this; an Ethernet connection is preferable, though you will also be able to use an AirPort connection, albeit at slower speeds.

Step 15 – Migrate over your information.

As part of the setup for your new installation, you will be asked if you wish to import data from another disk; you will want to. Attach and select your clone or Time Machine backup and Migration Assistant will bring over your data.

Step 16 – Enjoy your new installation.

Once migration has completed, shut down your computer and disconnect your clone. At this point, you will have OS X running on a Fusion drive on your computer. You can now use it like you would any other drive.

Things to consider before committing to a Fusion setup

As with any drive setup, there are pros and cons to a Fusion array. The pros, as mentioned at the beginning of the article are that it appears single volume and works automatically to keep the best speed. However, there are a couple of cons that you should also be aware of.

You will need a backup.

While a backup plan for your computer is something you should have anyway, this becomes even more important for Fusion drive equipped Macs. The way Fusion is set up, if either the hard drive or the SSD fails, the data on both drives is lost. Having a reliable, frequent backup plan will be essential in protecting against data loss.

Performance may not be enough for high-end professional use.

Apple claims near-SSD performance for Fusion-equipped drives. For casual use (email, Web browsing, basic iPhoto use, etc.), this is largely true. From testing both in-house and by Lloyd Chambers of Mac Performance Guide, a Fusion drive will first fill the faster SSD portion, then start filling the slower hard drive. Once writing is complete, data will be moved from the SSD to the hard drive until there is 4GB free on the SSD again.

The trouble comes when you start working with larger files, such as with pro audio, video and large-scale photo work. Often, these files far surpass the 4GB size, so you will see fast SSD transfer speeds followed by a precipitous drop in speed when it transfers over to the hard drive. For a full rundown of testing, check out Lloyd’s writeup at Mac Performance Guide.

For those that a Fusion drive just isn’t going to be practical, you may be better served using a Hard Drive/SSD 2-drive setup with a relocated home folder. You reduce the risk of losing all your data at once, while still retaining a large portion of the speed/storage benefits of Fusion, but with more flexibility.


  • Will Disk Utility on ANY version of OS X 10.8.3 or later work to create a Fusion drive?

  • I wish there was a way to do this at the folder level instead of entire drive level. Does anyone know if there is a way to do that?

    For me, my iPhoto/aperture library makes the most sense to have fusioned — I wish I could give it some chunk of my SSD for a working space, and let it run the overflow onto another disk. Then, if I’m editing a project, it could move the files to the work area for me, and when those aren’t touched, roll the earliest used files off to the hard drive.

    That makes more sense for my usage – photos and videos getting fusion and leave the rest on the SSD.

    Is there a way to do this?

    • It is possible to do this on a partition level of the SSD instead of using the whole disk. In a sense that is what you are looking for. You could create 2 partitions on the SSD and use one of the partitions to create a fusion drive.

      The act demotion and promotion of files that you are working was tested by us
      and we could not find that activity to occur. It is recommended to manually manage your individual files between the SSD and HDD for best performance.

  • I have 09 MBP with Mavericks already installed. I am planning to replace the HDD with bigger 1TB and add an SSD by removing ODD. What would be the best option for me to create Fusion Drive? Here is what I was thinking of doing:

    1. Install both new HDD and SSD.
    2. Take out current HDD and connect it via USB externally, boot from it.
    3. Use Disk Utility and Terminal to format and create Fusion Drive.
    4. Use CCC to clone from old HDD.

    Should that do the trick? or should I go about another way. Any help is appreciated. Thanks!

    • We unfortunately have not completed our test yet to be able to confirm setting up Fusion through Mavericks OS.

      Also, we only recommend clean installations, we do not advise to clone.

  • Since it seems that everyone’s diy fusion drives fail after upgrading to Mavericks, I am holding my horses. But any tutorials on how to fix it and upgrade?

    • I have an 27″ iMac with the “self made” Fusion drive, the installation went without a hiccup, but, I cleaned and repaired my HD before the download/installation.

      • What year is your 27″ iMac?

      • Can you clarify what you mean by “repair”? Thanks.

        • The iMac is a mid 2010 model, with 12 Gig memory.

          By repair I meant that I used Disk Utility, clicking the buttons Repair disk Permisions and Repair Disk.

          And before that, I ran Cocktail to removed old caches, and general cleaning. Then uninstalled applications that did not use for at least a year and old stuff that cluttered my HD.

          • Thanks for the suggestions. That’s worth a try.

            • I have upgraded to Mavericks my Mini (late 2012) flawlessly. I hope that my DIY fusiondrive is working. Upgrade took (in my opinion) too long – 30 minutes of installing & 7 minutes of finishing installation.

              • On my late 2008 MacBook with OWC Data Doubler in the optical bay and a DIY Fusion Drive, the only way I was able to upgrade to Mavericks was to delete the Mountain Lion Fusion Drive in Terminal, reformat the disks, recreate the Fusion Drive using the OSX 10.9 disk utility, and then reinstall the operating system onto the newly created Fusion Drive. Repairing disk permissions and using Cocktail to delete old caches had no effect. However once installed, Mavericks does run very nicely. I will need to recalibrate the battery to determine if there is any increase in battery life.

                • Thanks for the reply! You’re the first to confirm that this article works with Mavericks’ disk utility. (We all knew it probably would but nice to have confirmation.)

                  This method is fine because it’s probably what I would’ve done anyway with a new os install.

                  • As discussed earlier, creating the USB boot drive is different from Mountain Lion. But everything else in the DIY Fusion drive from scratch installation process appears to be identical with Mavericks (with the exception that the gray fabric texture background on the utilities has been removed).

                    • A total rebuild of the DIY Fusion Drive and a clean install of Maverick’s plus migration?

                      Ouch. I hope there is a solution to the “free” 10.9 upgrade. Maybe wait for 10.9.1?

                      (Late 08 MBP with 750GB Momentus ST and 128GB Crucial M4 SSD.

                    • Having followed the posts here I was not expecting this:

                      On a MBP Late ’08 with a DIY Fusion Drive (128GB Crucial M4 in the Optical Bay and a Seagate 750XT in the Drive Bay) all has seemed to go well with the normal Mavericks upgrade via Software Update.

                      I did give the ML DIY Fusion drive a PRAM reset, a DiskWarrioring, a SuperDupering and a TimeMachining before setting out.

                      After downloading, the update took about 2 minutes, then an automatic restart, then a 35 minutes install, then about 7 minutes to finish up after another automatic restart… and then straight to the Maverick’s Desktop.

                      All seems stable.

              • Sounds about right. That was how long my installation required. Upgraded without issue.

              • Upgraded my Mac Pro, inside of which I had previously set up a DIY Fusion drive with two internal drives. Mavericks installed without a hitch.

      • I have a late 2009 iMac with a Kingston 120GB SSD (In optical drive bay) along with the original 1TB HDD, think it might work?

        • I think the install will work on any compatible Mac with a DIY fusion drive, but it just depends on how much work you need to do to make it work. For the 2009 iMac, you may need to do as I did by completely starting from scratch with formatted drives, and then reinstalling everything from a Time Machine backup.

  • No luck doing an upgrade on my DIY fusion to OSX Mavericks. It says, “This disk not available for startup”. Not sure how to fix it.

    • Can you list the specs of your hardware? It’s gonna take some testing byany people to figure out if this works with Mavericks. I hope it does!

      • I have so far been unsuccessful doing an upgrade of OSX Mavericks to my two DIY fusion drive-equipped macs. One is a 2011 Mac-mini currently running Mountain Lion with a 128GB SSD and 1TB HD. The other is a late 2008 MacBook currently running Mountain Lion with a 240GB SSD and 1TB HD (in the optical bay). When I try to install, the Macintosh HD is grayed out and it says, “This disk is unavailable for startup”. For both of these computers, the installation of Windows via Bootcamp has been very difficult, so I am trying to avoid having to wipe the disks and start from scratch. So I will try a USB fresh install on an already functioning fusion drive.

        I am going to try running this command to get the USB installer created (courtesy of tywebb13 on MacRumors):

        sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled –applicationpath /Applications/Install\ OS\ X\ Mavericks.app –nointeraction

        • Thanks for the reply. Let us know how it goes when starting from scratch. I’m interest to hear if the method in this article still applies for Mavericks.

          • I too have a self-made fusion drive but in a MacBook Pro late 2012. I had no problems with the update, just downloaded Mavericks from the App Store and it did its own thing.

          • I have discovered that this command works well to create a OSX Mavericks USB install disk.

            sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled –applicationpath /Applications/Install\ OS\ X\ Mavericks.app –nointeraction

            Restarting the computer and booting from the OSX Install USB give you the same Utilities menu as in Mountain Lion. However I appear to be unable to install Mavericks onto my already-running Logical Volume Group (aka DIY fusion drive). Even when booting from the USB drive, the Macintosh HD disk is still grayed out and says “This disk not available for startup”

            Next experiment will be to completely wipe the currently online LVG and build a new LVG and try the install that way, but I do not yet know if OSX 10.9.0 offers the same DIY fusion options as did OSX 10.8.3

            • Great! I’m looking for someone to be the guinea pig for creating a Fusion Drive from scratch in Mavericks. :)

              • I will try to create a new DIY Fusion Drive and install OSX Mavericks as soon as I get everything satisfactorily backed up from my Mountain Lion install. I wonder why the other guy with the DIY fusion drive in the late 2012 MacBook Pro was able to update his without problem? I do not understand the cause of the “This disk is not available for startup” limitation that I am experiencing with a late 2008 MacBook and 2011 MacMini. There must be a plist command which fixes it. I’m sure someone here will figure it out soon enough.

  • I’m in the “thinking about it” stage of implementing a Fusion Drive on my Mac Pro 2 x Quad Core 2.8GHz (Early 2008), and have some questions:

    1 – My Mac Pro has 3GB/sec SATA connections in it, so I’m a little confused as to whether a 6 GB/sec SSD drive will work in this at the full speed of the Mac Pro – 3 GB/sec or will it actually step right down to 1.5 GB/sec. Quoting from a post on this page


    which said “I have an older MBP with a 3gb interface. I got a reply from OWC about which drives would work best for me. They said this: “While a 6G SSD does function, it will only do so at SATA Revision 1.0 (1.5Gb/s) speeds rather that the SATA Revision 2.0 (3.0Gb/s) speed the machine can deliver. Should owners of these machines desire another SSD option, the Mercury Electra 3G SSD does run at the full SATA Revision 2.0 (3Gb/s) specification.””

    So I’d be looking at an Electra 3G drive then?

    2 – I understand from reading the above, and the comments, that once a Fusion Drive is created I need to do a fresh install of Mac OS X Mountain Lion rather than cloning my current drive. My Mac Pro runs as a web server, so I have quite a lot of “customisations” done to things like httpd.conf, vhosts.conf, php.ini, my.cnf and no doubt other files I can’t remember – will a fresh install and then using Migration Assistant get all this stuff from the depths of OS X copied to the fresh install, or would I have to start all over again installing (where necessary) and setting up Apache, MySQL, PHP etc?

    (In the past updating Mac OS X and cloning my drives to ever larger drives has always preserved all this going back to Mac OS X 10.1 when I first started the web server to run my MySQL/PHP genealogy sites.)

    3 – comments on other brands of (usually cheaper) SSDs compared to the OWC drives?



    • The internal SATA speeds Inside all Intel Mac Pros from 2006 – 2012 all run at SATA II (3GB/s).

      Prior to the 2006 Intel Mac Pro, the Power Mac G5 does run at SATA I (1.5GB/s).

      I would recommend running your Mac Pro 2008 with an OWC 3G SSD as the the drive would run at the full revision of 3Gb/s.

      Yes, using migration assistant after the fresh OS install will transfer user accounts, applications, network and computer settings, and files from the original drive.

      • Thanks for the note on the SATA speed.

        As to Migration Assistant – yes I understand in general what it does, but what I don’t know in particular is if it reaches way in to the hidden files – in the etc and lib folders for example – to move over changed config files like php.ini, httpd.conf etc etc, or whether as I kind of fear, I’ll have to rebuild my Apache/MySQL/PHP server from scratch afterwards.

      • Another thought that is occurring to me – the merits of Fusion Drive compared to keeping the 2 drives separate, and running Mac OS X (plus all my web server stuff) from an SSD and keeping my User folder with its >500GB of pictures, 150GB of documents etc on a separate HDD. Same number of drive bays used up, and I can clone my current system over to the SSD with SuperDuper or CarbonCopyCloner and retain all functionality of my web server.

        I’d welcome any thoughts on the merits of this – Fusion Drive versus an SSD and an HDD as two separate drives?



  • So I followed this guide and set up my iMac with a Fusion Drive. I’m a bit skeptical, I found some applications that openned at lightening speed after I did my system migration initially are now loading slowly at hard drive speeds again, and to confirm the drive was audibly seeking as well during the apps loading.

    I am absolutely sure I have properly created a Fusion drive as above, using the diskutil from 10.8.5, on a USB stick made from the ML 10.8.5 installer.

    This makes me wonder if my fusion drive, created using MacOS 10.8.5 is actually moving frequently used files and apps onto the SSD at all?!

    How do I test it to prove it is moving frequently used files back to the SSD properly and vice versa?
    Is there an easy way to do this without having to wipe drives and start again.

    I just want to know its doing what it should be, otherwise it might be better to defuse and just put OS and apps on SSD and data on HDD and setup MacOs accordingly.

    Thanks in advance.

  • I wonder if you can offer me some help. I have a late 2008 MacBook 5,1 with a 1.0TB hard drive and a 240GB Mercury SSD installed. I have created my own fusion drive without any problem. It works well.

    Here is the problem. I went into the GUI DiskUtil with the DeBug menu enabled and was able to delete the OSX Boot from the HD. This meant that when I restarted the computer with the option key depressed, I only got one Macintosh HD volume (instead of 2). So far so good. So I went into GUI DiskUtil again and was able to reformat the 650MB portion which was the duplicate OSX boot into ExFat and renamed it BOOTCAMP. Then I went into Terminal DiskUtil and I resized my LVG to 1.1TB (it had been 1.2 TB).

    Unfortunately, I cannot figure out how to expand the BOOTCAMP portion to larger than 650MB. So now I have a 1.1TB Fusion Drive, a 650MB BOOTCAMP drive, and 125GB of free space which I cannot reclaim. The partition function under GUI DiskUtil is grayed out. Bootcamp assistant will not run.

    Any suggestions?

    • The Boot Camp Assistant will create the partition for you. You will not want to create the Windows partition from Disk Utility. It sounds like you will need to break the Fusion drive and set it up again, then use the Boot Camp Assistant to create the partition.

      • I have re-made the Fusion drive on a MacBook Aluminum using a Mercury SSD/Data Doubler and Toshiba HD. The optical drive has been removed from the computer. Now I want to install Windows 7 on a portion of the hard drive. When I open Bootcamp Assistant, it says, “You need an optical drive to install Windows–Connect an optical drive to your computer. You can’t install Windows without a remote optical drive”.

        My genuine Apple External Superdrive will not work on this computer.

        On my 2012 iMac I created a Windows 7 USB install disk, but the 2008 MacBook will not recognize it.

        Is there some way to modify the permissions so that this computer will allow me to either use the External Superdrive or to install Windows 7 from a USB?

        • Actually, I think I just figured it out. When I go to my Applications folder and right-click on BootCamp Assistant, I can open the info-plist. In the entry PreUSBBootSupportedModels there are a list of models which are supported. I changed the Macbook8,1 to read Macbook5,1 instead, and now I am able to use a UBS install.

  • Hello, just posted this as a CS Request, then thought it may have broader interest:

    Got a OWC Mercury Electra 3G SSD installed in a MBP 6,2 w OS X 10.8.5, and teamed with a HDD as a Fusion Drive.

    I tried to update the firmware using a USB flash disk, following the instructions. It will not succeed, giving methe following error messages:
    “Sorry, the firmware file appears to be damaged.”
    “Updating FAILED. Unable to find compatible firmware for your drive.”

    I tried to download the updater again, to install it on the flas disk, re repartition the flash disk (and testing it in Tech Tools 7), all with the same result.

    The SSD presently has firmware revision 501ABBF0, and I understand it is highly recommended to update…

    Is this a problem because of the Fusion Drive set up, or something else?
    Any advise on how to proceed would be appreciated!

    Thanks, and best regards…

  • Can’t see this question asked anywhere else.

    I currently have 2 dives in my MBP. An SSD and HDD. I have been fine using them (one for apps and the OS and the other for documents etc) TimeMachine backs up both drives.

    If I wipe both drives and create a fusion drive, how would this work with TimeMachine. Would it know that it should put everything from the 2 drives onto 1 drive?

  • Hi OWC, I scanned the comments and didn’t see this addressed anywhere, so apologies if it was already discussed….. Would it be possible to accomplish the same thing with removable flash storage, say a 128 or 256GB SD card on a Macbook pro? I’ve seen lately there are ‘short’ versions of SDXC cards that are intended for use in notebooks so they don’t stick out of the chassis, and as long as you didn’t remove it, it could serve as a ‘permanent’ drive for backups or perhaps ‘fusion drive’ type use. Is this possible, or is this limited because of the bus/interface for this type of storage? Thanks!

    • External drives have been reportedly tested to work with this DIY Fusion. Internal drives should be the preferred method for setup though, if an external is accidentally disconnected while the fusion is in use it will result in a data corruption.

  • I am having problems creating a Fusion disk in my iMac, its a 27″ 2010, with a 1TB HHD and a 60GB SSD
    I have both drives empty and unnamed, formated as1 partition, GUID Partition Table
    I have the latest System Installer on a USB flash drive and it boots from it. but I havent been able to proceed because when I’m in Terminal, after typing:

    diskutil cs create drive name driveIDs

    I get: “could not find disk for driveIDs”

    I have re-formated both hard drives again but still get the same response.

    Any guidance would be appreciated.


    • You’ll want to double check the driveIDs are being properly typed in and with a space inbetween the two driveIDs. If you continue to have an issue, I would recommend you reformat the drives as free space and try again.

      • Ben, you lost me when you said: “You’ll want to double check the driveIDs are being properly typed in and with a space in between the two driveIDs.”
        Are you telling me that when I type: “diskutil cs drivename driveIDs” I need to type the drives names instead of “driveIDS”?
        And then you mention to reformat the drives as “free space” is that instead of the GUID partition? or how do I do that?
        I’m clueless in this field (as you might now see).

        • Hector, you need to look closer into the instructions for step 11. As explained in the instructions, drivename and driveIDs are placeholders in the command for the name for your fusion drive and the IDs of the drives that will make up the fusion drive.

          Step 11 – Create the Fusion drive array.

          In Terminal, type: diskutil cs create drivename driveIDs

          This is the command that actually tells your Mac to tie the drives together in a Fusion array.

          Broken down, the step does this:

          diskutil – the command-line version of Disk Utility.
          cs – this invokes Core Storage, which is necessary for Fusion.
          create – creates a Core Storage group.
          drivename – this is the name of the drive and how you want it to appear in Disk Utility (not the Finder – that comes later). You can call it whatever you want; in our example, we named our Fusion array “Fusion.”
          driveIDs – these are the drive IDs of the drives you want as part of your Fusion array, separated by a space. In our example, they are “disk0” and “disk1”, but it may be different in your setup.

  • Hi there! I have 2011 imac with 3tb hdd and 120gb ssd installed. Now I’m trying to create fusion drive. As soon as I write first line of command in The terminal (diskutil cs create Fusion disk0 disk1) I get error 69886: invalid request. I think I got even another error msg one time saying the drive was unmountable.

    Please help!

    • This is most likely being caused by a bad command. Double check to make sure the drive ids are correct. If the issues persist, I would recommend to reformat both drives as free space and try it again.

  • I’d like to do this with my current 2010 27″ i7 iMac. Is it possible to do it this way:

    1) Clone my 1TB 10.8.5 drive with SuperDuper! to an external backup, then disconnect the backup.

    2) Install a new 250GB SSD.

    3) Boot to the 10.8.5 installer on a USB drive and create the Core Storage volume across the SSD/HDD.

    4) Install 10.8.5 to the new volume.

    5) Reconnect and boot from the external clone and use SuperDuper! to clone back everything to the new Fusion drive, overwriting the new install.

    So basically, I’m just modifying your instructions to use SuperDuper! cloning instead of Migration Assistant. I have a lot of dev environment software installed via CLI that I’d rather not reinstall and I don’t trust Migration Assistant to bring it over correctly.

    The second part of my question is, is this better than just putting my /Users folder on the HDD and the rest of the files on a 250GB SDD? Does a larger 250GB SSD make the Fusion’s ease of use more atrractive? Keep in mind that I’m coming from an HDD only, so either should be faster than my current setup.

    • If you’re just going to overwrite the OS you just installed, what’s the point of writing it in the first place?

      • I thought you had to do the OS install on the new Core Storage volume in order for it to officially bless it as a Fusion drive and also so the recovery partition it creates definitely has the updated version of Disk Utility. Is that not correct?

        • Oh! That’s possibility. I’ve not done it yet, but it’s on my list, so that’s good to know. I’d probably do a fresh install, so that’d be okay, but now I want to know.

          I thought at the end of step 13 (before your installed the OS) it was now “blessed”. I’m sure someone who knows will chime in….

    • We only recommend following the instructions we have outlined in the blog. Boot clones and clones in general are good for general backup, but for a clean setup of a Fusion drive we only advise restoring via Time Machine or Migration Assistant.

      I personally enjoy knowing what speeds I can expect from the drive I am working with. I agree that Fusion Drive offers some great features for average users, however prosumers and professionals should stick with independent SSDs and HDDs for maximum performance and flexibility.

      • Thanks, that’s good to know as I fall into the latter group and like a little more control. So your recommendation would be to keep them separate and move my user folders to the HDD and keep the system on the SSD? Does your video tutorial linked to above still apply for Mountain Lion?

  • Great tutorial! Thanks.

    Before I get to it, it would be great if you could help me a bit.

    I currently run Lion and understand I need to upgrade to Mountain Lion to build a Fusion drive. My Mac is a MBP Mid 2009.

    From what I understand, I would do the following steps:
    1) Purchase Mountain Lion and put it on a stick or SD card
    2) Make sure to have an up to date Time Machine Backup
    3) install the SSD, create the fusion drive and install ML
    4) use my backup to get all my files, programs and settings back on my Mac

    Alternatively, I could:
    1) upgrade to Mountain Lion
    2) backup
    3) install SSD & create fusion
    4) reload the backup

    Any comment´s are highly appreciated, including better alternatives.

    Many thanks

  • I have executed the setup noted above and have been relatively pleased with it. I am technically proficient but not a hacker.

    One thing I have noticed is that the Fusion setup is noticeably slower (not looking at technical data, just using the computer) than my prior setup, which was to have the OS everything except /Users on a 64 GB SSD, and /Users on a spinning HDD.

    To some extent, I should have expected this, but it’s frustrating to have my computer run slower under this setup. My question is — will the computer run faster if I swap my 64 GB SSD for a bigger one? I’m not sure how to think about that question.

    I appreciate the help!

    • The computer theoretically should run faster with a larger SSD. A larger SSD will mean more of your files will be located on the faster SSD, rather then the slower HDD. Some thing will be faster, however it all depends on whether the files are on the SSD or HDD. Your previous setup is our recommended setup for professionals and individuals that want the best performance and do not mind manually managing their files.

  • Awesome tutorial OWC!

    Question… Since my 2012 iMac i5 came with a 5400 rpm drive (looks like a SATA II drive running at 3GB interface) and my new SSD is a SATA III (6GB interface) does the entire fusion drive get dumbed down to 3GB? I’m assuming that all interaction with the SSD will go at the faster interface speeds, but since this is effectively “one drive” now I thought I would ask. If so, would it make sense to upgrade my slower SATA II internal drive to a SATA III before installing the SSD? Trying to get the best performance possible.

    Any feedback you have would be great! Thanks!

    • The Fusion Drive is designed to have all the day-to-day read/writes happen on the SSD and then it demotes files that either don’t get accessed often or don’t take advantage of faster read speeds to begin with to the HDD. So basically, the vast majority of read/writes with the HDD are done as background processes so you shouldn’t see any performance hits with the HDD operating at 3GB/s and 5400RPM – It should feel just like your whole system is running from the 6Gb/s SSD.

      • Thank You Michael. I was hoping that would be your answer. I knew both SATA interfaces were SATA III / 6GB, but Apple chose to throw in a crappy 3GB 5400rpm drive. But if my SSD will be the buffer for the whole system with the fusion setup, than it shouldn’t matter.

        Does Apple always use these cheaper/slower SATA drives with their fusion setups as well? New iMacs, etc?

        I’m thinking that it really won’t matter… but as a “techie” i might replace that 5400rpm 500GB SATA 2 drive with a SATA 3 drive as well. “Just cause”.


      • Last question…

        Since the SSD is the primary drive for all I/O, and will fill up eventually, does the performance of the Fusion setup drop when the SSD gets filled up more? I know that on existing SSD drives, I do see the performance drop down once it is 1/2 full, 3/4 full, etc. From this post it looks like the system will always keep 4GB free, but on my 240GB SSD, that’s roughly 98% full right? Just curious how apple’s fusion drive logic is handling that, and still maintaining SSD-like I/O performance.


        • From our testing, we found that it only slows down once the SSD is full and real-time read/writes need to made to/from the HDD. Granted, this really should only occur in a testing scenario where we’re purposely trying to overfill the SSD as fast as possible in order to force those read/writes of the HDD to become a foreground action, rather than run quietly in the background.

          • Gotcha. So in reality, when would the SSD become full? Only once the HDD is already full? My understanding is that the SSD will also keep the most frequently used/common files on the SSD for performance, but I did wonder how the SSD would get to a full state or how it manages to avoid becoming full and utilizing the HDD more often.

            Awesome information guys. I’ll be installing/setting up my fusion drive tonight. Can’t wait.

            • From what we’ve seen, the SSD is used solely until it is full – then files are moved off the SSD to the HDD in 4GB blocks. So in reality, the SSD becomes full as soon as that SSD capacity is met, then the last 4GB gets offloaded to be filled again.

              Flash storage isn’t like platter-based hard drives where as the closer you get to full capacity, the slower it performs.

    • I would think that the question is centered on what version of SATA bus is in the Mac. Buying SATA III drives is useless if the Mac just has a SATA II bus.

  • QQ: I just tracked the serial number of the Mac Mini I purchased from Apple last month, and learned that it was produced in June, 2013, but was unable to determine which OS was originally installed.
    I am currently running OS 10.8.4, and from what I can decipher in my logs, it looks like I started with 11.8.3 installed.

    This article was written in March, and warns of the perils of trying to install fusion drive when starting with a machine that originally ran 10.8.2 or older.

    Are we now out of the woods on this issue with newer machines?
    Can those who have a mac manufactured after a certain date assume they have 10.8.3 or newer and simply add a SSD and configure fusion drive without being concerned about having the wrong version of Disk Utilities?

  • I did this over the weekend – MacBook Pro 6,2.

    A couple notes and a question.

    Install went great – up thorough the creation of the drives and the start of the restoration. I would reboot from the recovery USB key – would get a message “the installation could not continue” or something like that. I did a search and the solution was to reset the PRAM (been a long time there – Cmd/Opt/P/R keys together on a reboot). That fixed it!

    My question – when the computer re-booted, I didn’t install the OS on the new Fusion drive – I restored from a Time Machine backup. Is my MacBook moving files around, or do I have to re-install the OS to make it “know” to move the files around to speed up the computer?

  • Thank you for the tutorial. This is confirmed working in 10.8.4

    Booted from a 10.8.4 USB flash drive
    Internal HD in my iMac as main storage
    External Crucial M500 SSD connected via Seagate backup plus thunderbolt adapter as SSD

    Works perfectly so far. It’s only been a few days

  • Hi! great work!
    after creating the FusionDrive (i’m using 10.8.4 and the drives are in an old mac via fire wire) is it possible to install 10.7.5?
    the mac with the ssd and the disk do not run 10.8

    If i boot from10.7.5 and run diskutil cs create name disk0 disk1 i get “invalid request error”

    thanks in advice

  • I have a 1TB Seagate SSHD (the hybrid drives) and a stock Apple 750GB HD in my mac mini. I would love to do this fusion process, but I’m questioning whether the OS will recognize the SSHD like it would an SSD. Best case scenario would be that it would fill up my 1TB SSHD drive and then start putting data on the second drive. Will this work do you think?

    • Setting up a fusion requires a true SSD, not a hybrid drive.

      • I am having a hard time understanding the difference between a run-of-the-mill CoreStorage drive and the “fusion” version of a CoreStorage drive. They are both Logical Volume Groups, right? So standard CoreStorage is the same thing as JBOD–in other words you’re just combining together two or more physical drives into a single virtual drive? And a “fusion” CoreStorage prioritizes one drive as primary and moves data to the primary faster drive?

        • Doesn’t look like you’re having a hard time at all. You defined it perfectly.
          CoreStorage is a single volume spanning multiple disks.
          A Fusion Drive is a CoreStorage volume that spans one SSD and one HDD which gives priority to the SSD and uses automated storage tiering to promote oft used files to the SSD, while demoting lesser-used files to the HDD.

          • Then to clarify, the following terminal command will create a standard core storage logical volume group WITHOUT any active rearrangement of the data. In other words, this command will create a standard JBOD logical drive?

            diskutil coreStorage create myLogicalVolGroup /dev/disk1 /dev/disk2

            Then is there another terminal command which creates a core storage logical volume group that specifies active rearrangement of the data? It seems that 10.8.4 brings with it some new terminal commands. Is there a specific termal command which specifies a fusion drive (i.e. a LVG with active data rearrangement)?

            • It isn’t a terminal command that changes the CoreStorage volume to a Fusion drive, but rather the OS installation in Step 14 that does.

              Essentially, what you’re doing through step 13 is creating a plain ole Core-Storage volume out of the two drives in such a way that the install of the OS is going to recognize and create the Fusion drive from. It is the whole reason that the version of Disk Utility found in 10.8.3 (or in the special build of 10.8.2 that came with the original machines that offered the fusion option) is absolutely essential.

              • Then it is the installation of 10.8.4 onto a CoreStorage drive which creates the “fusion” drive. Thanks for the clarification. So then what if your CoreStorage, instead of a SSD and a HDD, consists of a 7200rpm HDD and a 5400rpmHDD? Will the “fusion” process still shuttle more-often-used data to the faster drive? How does OSX know which drive is the faster drive? Is the order that you specify the drives when you create the LVG determine which drive is the primary drive? Therefore, if you do the process wrong, is it possible that 10.8.4 will move the more-often-used data to the slower drive?

                • In order for the Fusion drive to be setup, it needs to be a SSD and a HDD. Disk Utility can tell the difference between a Solid State and a traditional platter-based drive. Without one of each, it will not turn the CoreStorage volume into a fusion.

  • Hello,

    Currently, I have the following configuration:

    – Macbook 6,1 (Core 2 Duo 2.26GHz, nVidia 9400m)
    – 8GB of Mac-compatible (low-latency) DDR3-1066 RAM
    – 250GB HDD
    – OSX Snow Leopard 10.6.8

    I’m planning doing the following upgrade:
    – removing the 250GB HDD and installing a 500GB one;
    – installing the OWC data doubler with a 120/128GB 3G OWC SSD;
    – doing a clean install of ML 10.8.3

    My question is: does the MLion installer provide the terminal utilities you show in the tutorial for creating the fusion volume? In other words, I’m looking for doing a clean install of ML10.8.3 directly in a machine which previously had SL10.6.8. Also, I’ll not keep the hdd where the SL installation was placed. Will this plan work?


  • One question… It is known that if you install an SSD in addition to an already existing HDD and then use Disk Utility from the Recovery Partition that you will be prompted to repair the “broken” Fusion Drive. Isn’t that good enough? Why do I need to create the Fusion Disk within Terminal if Disk Utility will create it for me?

  • Please HELP!

    I have just finished creating a Fusion Drive using the DataDoubler on my MBP 13″ mid 2012.

    Everything was going perfectly until the Step 14 of your guide (http://blog.macsales.com/17624-os-x-10-8-3-provides-fusion-drive-setup-option-for-non-fusion-drive-equipped-macs).

    When I tried to install the OS X 10.8.3 from a USB bootable Key, The message “Can’t download the additional components needed to install OS X”.

    I have a perfect working internet connection, that I tested on the Safary browser.

    So please HELP, I am desperate. I have been working on this since 4 days and I really need my computer back to life!!

    Thank you!

    • There’s a couple things you can try.

      First, if you are trying to install over a WiFi connection, try connecting via Ethernet before you start the installation. If this fixes it for you, consider yourself lucky.

      What I’m suspecting the issue to be is that your USB installer is missing a recovery partition and you’ll need to re-download Mountain Lion from the App Store in it’s entirety and install from there. Use Command+Option+R during boot to access internet recovery mode to begin the download and install. As the download is about 4.4GB, it’ll take a while.

      If you’re still experiencing issues after that, please feel free to contact our Technical Support Team at 1(800)275-4576 via email or live chat.

  • Great run down. I always rely on OWC info as a great source and thoroughly researched writing. I have a question. I’ve installed a Seagate 2.5″ ST1000LM014 that incorporates flash and spindles. I’ve then installed a 128GB SSD from Samsung. Will the the core storage be clever enough to make use of the flash from the seagate and the SSD?

    Apologises if this question has already been asked. I did look but couldn’t see a post.

    Thanks in advance.

    • This isn’t anything we’ve tested specifically. However, as the transfers from SSD to HDD and vice versa are background processes, there wouldn’t be any noticeable difference in performance. Additionally, as far as the Fusion setup is concerned, the 8GB of NAND flash in the Seagate Drive would be seen as part of the HDD partition. So, I don’t believe the Fusion setup would incorporate that extra NAND as part of the SSD.

  • I got to the last step and got a error saying:

    error -69822: couldn’t rediscover disk after operation

    any suggestions- I have tried it about three times and cant get it to spit out the line I want which is ” Formatting file system for logical volume, etc” ??

    • The error message you are seeing is different. It is very important to make sure you do not have any typos with spacing or the groupstring. If the issue persists the best thing to try is to delete the CoreStorage logical volume group and try it again. To delete a logical volume group use the following command line: diskutil cs delete groupString. Next Run a free space on the drives within Disk Utility.

      “Free space” is an option for formatting the drive in Disk Utility:

      Choose the drive you’re looking to “free space.”
      2. Under the Partition Tab choose Volume Scheme – 1 Partition
      2. For “Options…” choose “Master Boot Record”
      3. The for “Format:” Choose “Free Space”

      Before reattempting the Fusion creation it would best to verify both the SSD and HDD are fully functioning. Running a verify disk on the drives from Disk Utility or an integrity verification for the HDD through Speedtools or Drive Genius.

  • Question: If I were to install a PCI SSD drive (like the one’s you sell on the site) could I use that as part of the fusion drive? Just target it in the set up?

    • The Accelsior can be used to create a Fusion drive. Please note, it is important to remember that the Accelsior is a RAID 0 of two SSDs.

      By creating a Fusion drive using the Accelsior you are then relying on 3 drives to maintain health. if any fault occurs between the 3 drives the whole Fusion drive and data will be lost. This is why maintaining a consistent backup is highly recommended.

  • I cloned my hdd to an external hd, is it possible to create a fusion drive and instead of installing a clean os x, can i clone the external hdd to fusion drive? I also have maverick beta install if i make a fresh install from beta 1 will i be able to upgrade to the latest beta without loosing the fusion? Thank u

  • After you have created the fusion drive, what’s the preferred method for later upgrading one of the drives? Say in a year I want to get a bigger SSD. Is the only way to do this to destroy/wipe the Fusion drive, and then re-create it using the old HDD and the new SSD?

    Also, I have found that the fusion setup is noticeably slower for me than running the OS and applications off the SSD, and my /Users folder off the HDD. I presume that buying a bigger SSD for the Fusion array will speed things up; is that true?

  • If I have Snow Leopard 10.6.8 atm, do I need to upgrade the OSX before cloning/time machining? So I mean to say is should I have the current version of OSX Mountain Lion installed on my Macbook before even starting with these fusion steps??

    btw, I have a macbook unibody late 2008 2ghz 13.3 5,1


    • YEs, your best bet would be to upgrade the OS first.

      • Thanks Michael!
        Just one other question, if I decide not to create a fusion and instead run the two hard drives separately and I prompt my macbook to run startup disk from the SSD that is in the optibay (which has my OSX system on it) will all non-OS (word, excel etc) files saved in future be saved onto my SSD or HDD or will my mac decide that as it goes along?

        Im reluctant to create a fusion (also probably wont need it for my use) however Im worried that without the fusion of the two drives, My mac wont manage data storage correctly.. I will ofcourse save any OS updates or othe OS software on the SSD directly.

        • Sorry just one other thing, will it be necessary to install Mountain Lion OS if I dont intend to fuse? will Snow Leopard handle the data doubler?

        • There’s three basic setups that you can do with a SSD & HDD internally.
          1. Use the SSD to keep your OS and system files, while keeping your data on the separate disk. You can set this up seamlessly by following the instructions in our TechKNOWlogy video here.
          2. If you have enough space on your SSD, keep that as the main drive and use the HDD as a completely separate volume (like having a permanently-connected external drive).
          or 3. Setting up a Fusion drive as instructed in this article.

          There are definite merits to each.
          The Fusion gives you a seamless way to let the OS store your data, but there is an increased need for current backups as if either drive fails, it will corrupt all the data on both drives.
          Keeping the drives separate means you have to manage which data is stored on which drive manually – which can be good or bad depending on how you’re using it – but it means that you decide where the data will be stored, not the OS.
          Relocating your home folder to the HDD and keeping system files on the SSD will speed up the overall system, and in case of drive failure does not affect the data on the other drive.

        • Nima,

          I have done what you are describing. It is pretty easy to set up, but I have found that over time, you will find little annoyances, like programs saving to the /Users folder on your SSD when you want them to save to the /Users folder on your HD. Anyhow, if you want to do it, I wrote the instructions up on my blog here:


          • Most knowledgable instructions about moving the user folder to a second drive state that after the folder has been successfully moved to the other drive and is functioning properly that the original user folder should be deleted. If it wasn’t there to confuse the OS in the first place, then there wouldn’t be such little annoyances.

  • Is it possible to raid 2 SSDs and then fusion them together with a larger traditional hard drive? And if so what do I need to do? Thanks!

  • If these DIY fusion drives do not perform smart migration (“promoting” oft used files to the ssd), then I’m not sure what the advantage is. It seems to me that it would simply give you fast write times (and fast read times of just used files) while working, but once data has been transferred to the hdd there would be no benefit (besides the system and program files being on the ssd). Am I missing something?

    Also, how are you testing or trying to verify smart migration?

    • Your basic premise is incorrect. Following the instructions above results in a fully-working Fusion drive (with the data migration).

      You can watch the transfers using the iostat command in terminal.

      iostat disk1 disk2 1 [where disk1 & disk2 are the drive identifier of your HDD and SSD] will provide an output of disk activity on each drive every second. Running this while writing data to the drive will show all the activity on your SSD until that drive is full, then it will show it starts writing to the HDD. Once your block of writes are completed, if your Fusion Drive is setup properly, you will see activity that transfers about 4GB of data off the SSD over to the HDD.

      • So, I am confused. OWC Ben wrote on this blog on June 3, 2013,

        “There have been reports of frequently used data being moved to the SSD while infrequently used data is moved to the HDD, we have not seen any proof of that in our testing.”

        That is what I am talking about when I say smart data migration with frequently used data being promoted from the HDD to the SSD. In your post on July 31 it appears to me you meant data migration from SSD to HDD (keeping 4gb free on the SSD). I am talking about the other way around – HDD to SSD. If the DIY Fusion drive does not do this promotion of frequently used data from the HDD to the SSD, what is the advantage, besides fast read/write times of data in the current working session and system files/applications on the SSD? Isn’t this what Apple said the Fusion drive does – transfer frequently used data from the HDD to the SSD? If the DIY Fusion drive does not do this, how could it be a fully-functioning Fusion drive?

        When you say the DIY Fusion drive created by the steps listed in this blog is “fully-functioning Fusion drive,” do you mean it is fully-functioning EXCEPT for the data promotion from HDD to SSD? Or are you saying that even a Fusion drive shipped from Apple does not do this? Apple claims that their Fusion drive DOES do this (see the video of Phil Schiller explaining it: http://www.youtube.com/watch?v=NPP1ddcEkmE).

        • We are currently taking a closer look into this smart data migration. Results hopefully to come in the near future.

          • has there been any update on this?

            • I’m still currently testing this. I have been able to see a file being demoted from the SSD to the HDD after repeated filling up the 4GB buffer space. I have not seen any proof of a file being promoted to the SSD from the HDD so far.

              • Thanks for testing this. I am interested to hear the results too.

              • Any updates? Debating if i should go the fusion route or use the SSD to keep my OS and system files, while keeping my data on the separate disk.

                • I’ll have a full blog post on my finding hopefully towards the end of next week. I am currently replicating my testing on a Mac Mini that came with a fusion drive from Apple. In my testing on the home-built fusion drive I was able to see a video file that was on the SSD demoted to the HDD. I was unable to see this video file promoted back onto the SSD though. I’m testing this procedure on an Apple Fusion drive to see if there is any difference between the home-built fusion and the prebuilt Apple fusion.

                  • Any updates on this question?

                  • Before going with the fusion drive setup I used the SSD for system and apps and the HDD for User folder. It worked OK. But the fusion drive setup is much smoother (on my Late ’08 MBP.)
                    Though the fusion drive setup comes with the risk of: either drive fails, everything lost. So Time Machine and updated clones are a requirement for me.

  • Is it possible to enable noatime on a fusion drive?

  • I have a windows partition on my 1TB internal HDD in my iMac, I’m trying to avoid opening it up and i have a 128GB SSD connected through thunderbolt, if i set up the OSX partition and external SSD in fusion, will it wipe all the partitions on the 1TB drive? Thank you.

    • No matter the configuration when a Fusion drive is setup between two drives the data on those drives will be erased. You will need to back everything up before setting up the Fusion drive.

  • I assume that while the article mentioned 10.8.3 that the current 10.8.4 download works as well?

      • Thank you and since I’m not sure about the architecture of MY MacBook Pro 2012 ( 9,2 ).
        I’ve got 2 questions:
        1) Is there a preference as to if I put the SSD or the hard drive in the CD carrier? (I thought I read there was a throughput difference on some models).
        2) I assume the Electra 6G and the Extreme Pro 6G will work, but for the extra money will I see a performance increase with the Extreme Pro 6G?

        • 1 – Given that the 6Gb/s bus speed is reliable in both bays (15″ models natively supported 6Gb/s in the optical bay, while the 13″ models were supported after a firmware update), I always suggest installing the traditional, platter-based drive in the main hard drive bay to take advantage of the SMS (sudden motion sensor) that will attempt to park the drive in the event of an accidental laptop drop.

          2 – Yes, either will work. For the extra money, the OWC Mercury EXTREME Pro 6G is optimized to handle incompressible file types like those used by high-end audio, video, and photography. So if you’re using the laptop primarily for high-speed audio, film, photography, and graphic production, then the additional performance will be noticeable. For most other usage that reads/writes compressible file types, the Electra 6G is going to perform just as fast as the Extreme.

  • if i have a 128gb SSD and 320gb normal drive, what size does the fusion drive become?

  • Can the Mercury Accelsior_E2 be used as the SSD in a DIY Fusion drive, as described here, or only with special steps, or not at all?

    This would be in a Mac Pro 4,1 (early 2009) that has about 500 GB of music from CDs and 250 GB of OS, software, and other data, on the existing 1TB drive.

    I am already running 10.8.4, and using Chronosync to make bootable backups to external drives. Could I boot one of those in step 8, and then in step 14 make a bootable copy of it onto the new fusion drive, instead of the clean install? Do you advise for or against that approach? Why?

    • The Accelsior can be used to create a Fusion drive. It is important to remember that the Accelsior is a RAID 0 of two SSDs. By creating a Fusion drive you are then relying on 3 drives to not have any issues, if any fault occurs between the 3 drives the whole Fusion drive and data will be lost. Maintaining a consistent backup is highly recommended.

      We only recommend following the instructions we have outlined in the blog. Boot clones and clones in general are good for general backup, but for a clean setup of a Fusion drive we only advise restoring via Time Machine or Migration Assistant.

      • Thanks for persuading me not to try for shortcuts. Starting with 10.8.4, and downloading the full installer for 10.8, the directions worked as stated, with the following minor variations:

        1. In steps 3 and 5, dragging to the desktop generated an alias, which could not be used for the next action. I just worked on the original, in place.

        2. In step 9, the natural location for me to launch Terminal was from the menu.

  • I have a 256GB SSD + 1TB HD in my MBP. It was working fine for months and then I needed to reinstall the OS and things went sideways. I decided to restore from backup and have not been successful, so I rebuilt the Fusion drive and used the Migration assistant to copy my files over. Things seemed fishy when it said it would take 7 hours and then finished in 45 minutes. It got to the part where you create an admin account and then hung once I entered the info. I’ve tried twice with the same result, so I’m wondering what the issue is.

    • There are a quite a few variables with this issue unfortunately. It would be best to break the Fusion drive and test each drive individually to see if you can isolate an issue with one of them. You also want to be sure to run a few tests on the backup drive to make sure that is not corrupted or having any of its own issues.

      • I was able to get up & running again with the 1TB HD alone. I can format the SSD, install OS X on it & restore my files, but can’t get the Fusion to work. I get as far as restoring from my TM backup or SuperDuper clone and the restore always fails about 5GB in.

        Not sure what else I can try. Every way I can tell, both drives are fine & I was able to restore from the TM backup onto the HD.

        • I would try installing the Mac OS onto the Fusion drive first. Do not try to migrate files during the initial setup process, I am ONLY recommending this since you are experiencing issues. Create a “Test” user account at the end of the initial setup, it is very important you do NOT create a user by the same name that you will be transferring. Once you have booted into the Test user run your Mac OS updates until there are no more updates. You can then attempt to migrate your files with the Migration Assistant application, this is located in the Utilities folder which is found in the Applications folder.

  • I do have a question about the cloning process after the Fusion Drive has been created.

    Why is it that 1st you install the OS and then do a migration from a cloned drive?
    Why not just update the OS to 10.8.4, clone this update disk, boot to the 10.8.4 USB drive, create the Fusion drive, and clone back the original cloned drive (done Step 1) using the Disk Utility Restore and eliminate the migration?

    • OWC only recommends using Migration Assistant after doing a fresh Operating System install

      • Is it possible to erase and do a clean install to “a” fusion drive? Will it maintain its fusion state throughout the erase process?
        How does it know that it is “a” fusion drive?

        • Yes you can erase and do a clean install on the Fusion drive.

          After erasing the Fusion drive Open Terminal and Type: diskutil cs list

          This will give you a listing showing any Core Storage Logical Volume Groups (aka Fusion drive).

          To verify your Fusion drive is running properly I would recommend running tests on the new Fusion drive to see if it is behaving like a Fusion drive should.

  • Just wonder about TRIM in the SSD, is it enabled automatically or does it not matter at all in this configuration?

  • On a MBP Late ’08 with a 128GB Crucial in the Optical Bay and a Seagate 750XT in the Drive Bay all seemed to go well with the Fusion setup.

    But I am left with a very unstable Fusion Drive and do not know how to get back to my 2 drive setup? I want to revert to Apps and System on the SSD and the User folder on the XT. It’s not obvious in Disk Utility.

    • Since you can’t erase the volume that you are booted into, a boot disk when need to be created to boot from. I would recommend Apple’s OS X Recovery Disk Assistant which can be created on a Flash Drive.

      After you boot into the Disk Assistant, Open Terminal and Type: diskutil cs list

      This will give you a listing showing any Core Storage Logical Volume Groups (aka Fusion drive). You will need to copy the long alphanumeric string for the Logical Volume Group that is listed

      In Terminal Type: diskutil cs delete groupString

      The Fusion should now be deleted

      • If that Terminal commend removes the Fusion drive, what will be left of the two drives that created the Fusion drive? What would you have to do in order to use them as separate internal drives, such as System and Apps on the SSD and data on the HDD?

        • To properly setup 2 drives that are not Fusion drives I would recommend following these directions 

          Next Keeping your System and User files on Separate Drives i would recommend following these directions

          • Eddie, this didn’t answer my question at all. What I asked was how to format the two drives; a SSD and an HDD that were previously joined as a Fusion drive. Because in my recent experience you can’t do anything with them aside from making them back into a Fusion drive. Once they have been a Fusion drive, a Fusion drive is all that they can be.

            • If you ever want to “break” the fusion and use the drives separately again, make sure you have a backup of any data you don’t want to lose (breaking the Fusion will destroy all the data on the drives).
              Easiest way we’ve found is to unplug one drive, boot to internet recovery, then free space the drive. Then power down, plug in the other drive, unplug the one that was just free spaced, boot to internet recovery and free space it. That should then leave you with two drives that completely blank and ready to be used however you see fit.

              “Free space” is an option for formatting the drive in Disk Utility:

              1. Choose the drive you’re looking to “free space.”
              2. Under the Partition Tab choose Volume Scheme – 1 Partition
              2. For “Options…” choose “Master Boot Record”
              3. The for “Format:” Choose “Free Space”

  • Two things:

    First of all, I just successfully set up a Fusion drive using an externally connected Thunderbolt drive. It’s working fine. Except, for item number two:

    When I went through the process the diskutil coreStorage list command showed the internal SSD as Index 2 in the array, and the external Thunderbolt HDD as Index 1. This concerns me that perhaps the system is writing to the Thunderbolt drive first. What little I’ve found in my research has said that the Fusion system is smart enough to know which of the drives is the SSD (either by reading its performance, or by looking at the UUID) and handles all of that in the background. But do you know if there is a way to tell which of the physical drives has the most data on it? Thanks.

  • I decided that my Mid 2009 Macbook Pro with the successfully installed Fusion drive would run cooler if I switched the the SSD drive to the Optical bay and moved the Seagate 7200 rpm drive to the traditional Hard drive space. I did that and decided to see if the Fusion drive would still be intact and startup. It did! Amazing. Also the Macbook Pro runs cooler (less fan runnning and noise). No issues so far.

  • How does setting up a fusion drive on a MBP affect battery life? Does the HDD spin up and down a lot? Maybe there are power savings because the default write disk is the SSD?

    I am using a mid-2009 MBP, mostly for internet browsing, music, watching videos, editing documents (Pages, MSWord), typical consumer stuff.

    • We haven’t directly tested this, however setting up Fusion means both drives are behaving as one. This means that both drives are more likely to be running at the same time and drawing power. The most energy efficient approach would be to not setup a Fusion drive and manage the two drives independently.

      It is also a good reminder you can modify how quickly drives are put to sleep in your computer. We detail how to do so here

  • I’m not sure I would have attempted this without these great directions. A couple of notes that would have made it even easier is if the list of things you need at the beginning, and/or in Step 6, you mention that the USB drive needs to be formatted as a GUID Partition Drive. And then in Step 9, mentioning that you get to the Terminal by clicking on Utilities>Terminal.

  • I created a Fusion Drive last week. I am noticing a strange thing.

    My drive space is slowly filling up, without doing anything!

    I can sit and watch my “Get Info” for the disk, and it keeps getting larger. It seems to be several GBs a day.

    Any ideas?

    • I would recommend contacting our Technical Support Team at 1(800)275-4576 via live chat or email to help troubleshoot

    • I had a similar behavior recently but it turned out it had nothing to do with fusion drive but with a time machine setting creating local backups (a backup to your local drive when an external time machine drive is not connected). A description of the issue or feature plus how to detect if this is the problem and how to turn local backups off you find here: http://pondini.org/TM/30.html
      Otherwise you have to look elsewhere for the cause of the continuous storage increase.

      Good Luck

  • I intended to fuse up my 500gb had and 128gb SSS in MacBook Pro 15early 2001 2.0gb processor .
    The problem is, the last step to create volume. I stuck at 60% remaining during waiting for logical volume to respond. Not responding in fact. Please help.

    • It sounds like you have a 2011 Macbook Pro. Which ever drive you added to your optical drive please be sure it is a SATA II 3G drive. If you put a SATA III 6G drive in the optical drive you can expect to have issues with that drive both in Fusion creation and in general use.

      OWC Larry goes into detail about that issue here

  • I have a doubt, in the previous post you guys refered an article in which the author said no files were promoted to ssd an only ssd to hdd writes were seen. Is this still true? or the new version of disk utility in 10.8.3 allows the most used files/blocks to be promoted to ssd

    • This is a contended topic about Fusion drives. With our testing we have not seen any smart data migration between the SSD and HDD. Our testing has shown that a Fusion drive only maintains a 4GB buffer space on the SSD. When the data is written to the 4GB buffer on the SSD it will slowly write that new information to the HDD until there is once again 4GB of free space. There have been reports of frequently used data being moved to the SSD while infrequently used data is moved to the HDD, we have not seen any proof of that in our testing.

      • If these DIY fusion drives do not perform smart migration (“promoting” oft used files to the ssd), then I’m not sure what the advantage is. It seems to me that it would simply give you fast write times (and fast read times of just used files) while working, but once data has been transferred to the hdd there would be no benefit (besides the system and program files being on the ssd). Am I missing something?

        Also, how are you testing or trying to verify smart migration?

  • I need to replace an aging xserve which runs a busy email server, a few Parallels VM’s running Oracle, and a fileserver of tones of both active and long-term archive files. Total current space = 4 TB (3 x 2TB, internal Apple RAID-5). replacement server should be a little bigger – 5+ TB.

    I’m trying to hit 3 needs – Speed, Redundancy, Price. By price, my budget is about $5000.

    I’m considering the Areca 8-bay thunderbolt raid enclosure with 4x small SSD and 4xHDD, where the SSD’s are one raid 10 volume and the HDD are one raid-5 volume. I’d then like to combine them into a Fusion Drive.

    I’d like to get two identical Mac Mini’s, and reformat their internal drives such that there is no OS or data on them – just blank drives. I’d install the OS on a boot partition on the external RAID and boot from it, then run the rest of the server from it.

    I’d keep the 2nd mac mini on hand as a cold spare should the first one ever break down.

    I’ll back it all up with Time Machine to an existing Drobo.

    On paper, this sounds like a very high performance, very redundant setup, at a reasonable cost. Less expensive than the top-of-the-line xserve it’s to replace.

    Few questions:

    -Is it possible to make a Fusion Drive out of two separate raid volumes on an external thunderbolt enclosure such as the Areca? a real Fusion drive – not just two volumes slapped together.

    -any thoughts about running a server on a Fusion drive?

    -can you see any real dangers from the setup i’ve described?

    • The Areca 8-bay thunderbolt raid enclosure currently only supports booting over EFI Bios, so in a VM environment on a Xserve the Areca 8-bay thunderbolt raid would not be bootable. Also, Fusion technology is designed to work on internal drives only and would not be supported externally.

      OWC recommends running Fusion on consumer level applications vs. prosumer applications.

      • Hi, thanks. To clarify, the Xserve is being retired. it’s replacement is a mac mini with EFI Bios and thunderbolt, so i think that part should work.

        The VM environment is just Parallels running as an application under OSX, so i think it should be just fine too. I only listed it as it imposes a significant amount of time-sensitive disk I/O on the server.

        “Fusion technology is designed to work on internal drives only and would not be supported externally.”

        This is the part i’m most concerned about. I understand that it adds risk to, lets say, try to marry two external hard drives into a fusion drive. if one gets unplugged, it may corrupt the pair. But Fusion Drive, as it’s designed, marries two internal drives into one. The fear is, of course, that you’ve just multiplied your potential failure rate by 2, as either drive failing will result in total data loss.

        thus the hardware raid…. it fixed the danger of single drive failure decades ago. but low cost raid typically has no data tiering. high-end raid does, but not the low end stuff.

        As OWC sells the Areca raid, would I be asking too much for you to crack one open, install a couple of your SSD’s into it plus a couple HDD’s and take ‘er for a Fusion Drive spin? as the only 8-bay hardware raid with thunderbolt currently on the market (to my knowledge), and as OWC is in such a position of authority about all things mac, SSD, Fusion Drive, etc, you’re in the unique position of being able to really shed some light on this. At the least, it would make for an interesting OWC blog post. At best, it would propose a really powerful server solution applicable to many, many people – including myself, of course!

        Unless i’ve missed something, i don’t see what aspect of my plan is technically not possible. “unsupported” can mean so many things!

        • Ok, so I have a concern that may render my idea currently impossible…

          I’d like to know how a Fusion Drive knows which drive is the SSD and which is the HDD. Does it use SMART data, does it test to see which one is faster, or does it just go by whichever disk is named first in the command to create the fusion drive in the first place?

          If it uses SMART data to identify the type of media, then what happens when i put 4 SSD’s in the Areca array and create a raid set out of them… will the resulting raid set be identified to the Mac OS as an SSD, or an HDD?