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.


  • Noob question:
    Can I use the 10.10 Yosemite-installer or does it have to be the 10.8.3 installer and only that?

    • the feature was introduced in 10.8.3. 10.8.3 or any later version will work.

    • You are able to use 10.10. I would recommend reading our blog “Creating your own Fusion Drive”.

      This will allow you to install a fusion drive using 10.8.2 or later, including 10.10.

      When you partition a drive using Yosemite it creates a Core Storage volume. The easiest way to remove that is to format the drive using Windows or Mac OS 10.6.8 (Snow Leopard). Either of those methods will remove the Core Storage volume. After that you can use the Erase tab in Disk Utility in Yosemite to set the drive back to MacOS Extended Journaled without creating a Core Storage volume again. Once you have done this, you can proceed with the instructions from the article “Creating your own Fusion Drive”

  • How do I setup a Boot Camp Partition with my fusion drive?

    • Once the fusion has been completed you will want to use Boot Camp Assistant. Boot Camp Assistant creates the Windows partition on the disk drive instead of the flash drive (SSD).

  • Thanks for the guide. It worked perfect. Migrating my time machine data now. Only 7 hours…will update when completed.

  • I followed this guide with the slight variation of preserving the recovery partition. Unfortunately after several months of amazing performance, the computer started showing the beach ball for every selection. Disk utility gets a “File system check exit code is 8” and I did a “command key” and “R” to get into the OS X Utilities Disk Utility. The Disk Utility couldn’t repair my Fusion HD and stated I need to reformat the disk and restore from backup. I have the restore partition and I’m wondering what are the recommended steps to recover from this. I have a TimeCapsule so restoring isn’t an issue. Just wondering how to reformat and preserve my recovery partition. Thanks in advance. This isn’t has nothing to do with the OWC SSD or these instructions – it has to do with my main HD being 5 years old!

    • Sounds like you should replace your HD first.
      Afterwards, you can get back to a fusion drive again (with recovery partition), by doing the following.
      Run the OS X installer on the replaced disk. As part of the install, this will create the hidden recovery partition. You’ll be trashing the OS X install in the next step, so no need to worry about applying all patches and updates once you’ve run this install.
      Then create a fusion drive by merging the data partition of the new HD and SSD (using the modified instructions like you did last time). This will destroy the OS X install you just made, but will leave the recovery partition alone.
      After creating the fusion drive, boot from the recovery partition, and restore from your Time Machine backup onto the fusion drive.

    • One thing I would recommend is to use the Apple Recovery Disk Assistant to create a backup recovery volume on a thumb drive. This will give you something you can always fall back on to use to access the OSX Utilities operations so you can format a drive, install an OS, etc. without having to worry about preserving the recovery volume. In fact, being able to wipe the whole drive clean including the recovery and start from scratch can be instrumental in certain types of repairs.

      To fix a Fusion issue, or any corrupt volume, you can always try using that recovery thumb drive to wipe the boot drive totally clean with a reformat, install a clean copy of the OS, and restore your data from your backup. If the problem is due to a corrupt volume then it will be fixed. If it persists then it is more likely a hardware issue and you can do further tests to verify what needs to be replaced.

      If you have any further questions please contact our tech support team via phone at 800-869-9152, or 815-338-8685 internationally; by chat; or by e-mail.

      • Sent an email but didn’t hear back. I built a recovery disk assistant on a thumb drive and erased the main partition (is this the same as format?). When I went to restore from TC backup it gets to a point and seems to hang (has estimated time remaining at 3 days for a couple days). How do I reformat everything? Btw, I’m guessing the issue is my old HD so I bought a new 3TB drive from you guys. If I put the new drive in can I reformat my SSD and new 3TB drive and then recreate the steps to build the fusion drive, or do I have to do something to undo the fusion drive first?

        • I’m sorry you haven’t heard back yet. The best way to format the drive is actually to partition it instead of erasing. That will remove the volume information more cleanly. After that you should be able to set the drives into a Fusion and then install the OS to the Fusion volume.

          As for putting the 3TB into the setup with the SSD you already have, it would be best to contact Apple directly as they are the experts on Fusion and would be best able to provide options for breaking that manually.

  • I just wanted to confirm whether I actually have to purchase another copy of the OS in order to do this. I have a Mid 2011 27” IMac, I’m not sure what it came with but is the Disk Utility sufficient for creating an actual Fusion Drive so that I can skip the step of install the OS?

    Also, is there any reason that after fusing the drives I can’t just restore from my Time Machine backup? Why must you install the OS then use migrate?

    • Once you have downloaded the update in the App Store you can re-download the installer from your past purchase history any time you need it. You cannot just set up a Fusion in Disk Utility, you do need to go through the process in this article.

      Installing a fresh, clean copy of the OS and migrating has the best chance of making sure that everything goes smoothly for you.

  • Any caveats / drawbacks to doing this Fusion Drive setup with two internal SSDs?

    Specifically, I’ve got new 240GB OWC Mercury Electra 6G (6Gb/s) SSD in the main drive bay of my Early 2011 17-inch MacBook Pro, having moved the original Apple-installed 120GB 3G (3Gb/s) SSD into the optical bay using an OWC “Data Doubler.”

    Would the overall Fusion Drive be slowed down to the slower speed of the 3G?

    • The way a Fusion works is by combining two drives, one is a long term storage drive, the other acts much like a cache. The cache holds files you use frequently, as determined by the Fusion drivers, and files you are working on as well as allows for saving data quickly before moving that to the storage drive.

      OWC hasn’t really tested a set up like this, but from the way Fusion works you won’t get the results you are likely expecting. If set up properly, you will be limited to the 3G speed of the smaller drive. If you set it up to get the speed of the 6G, you will be limited by the size of the smaller drive. Your best bet is to keep the drives separate and manage the data locations yourself.

      • I believe I am getting the full speed of my Accelsior_E2 when paired in a Fusion drive with a 3Gbit/s HDD in my 2009 Mac Pro.

        If you specify the faster drive first, then the slower drive would only be used for data when the faster drive is down to 4GBytes free space. There won’t be much speed advantage (a bit less than a factor of two, taking into account the overhead), but there would probably be enough to measure and possibly enough to notice, and there would be a simplicity of management of a single “drive” from the user perspective.

  • I created a fusion drive using a macsales SSD in a mid-2009 macbook pro. It has worked very well—no problems. Now I have to go back to a complete backup (SuperDuper bootable backup). Do I have to reformat the fusion drive to restore a complete backup? if so, do I have to break the fusion drive, and start over? How do I reformat the SSD or do I? I’m still confused about trim. Thanks.

    • The best way we find to restore to a drive from an old drive, backup, clone, etc. is to use the recovery volume to install an OS and restore your data. You can also use the Apple Recovery Disk Assistant to make a backup recovery volume in case you ever need it.

      When you have to format a Fusion drive and remove all the data to start over it can’t hurt to break and remake the Fusion, but it shouldn’t be necessary unless something is wrong with one of the drives, or the Fusion itself.

      For more information on TRIM I’d recommend checking out our blog article on the subject. In short, TRIM provides useful maintenance to the SSD; the Apple OS doesn’t provide TRIM to most SSDs and any external SSDs won’t receive TRIM support as they are external. In order to keep the SSD in peak running condition you need something to replace TRIM in these cases. Our SSDs, however, take care of themselves and don’t require any external support.

      If you have any additional questions please contact our tech support team via phone at 800-869-9152, or 815-338-8685 internationally; by chat; or by e-mail.

  • Do you recommend doing the fusion drive on a Mid – 2007 macbook (the white macbook, not the Aluminium unibody one)? Would that be something possible?

  • The capacity of my Fusion Drive, as given by Command-i, is 860GB (a 750GB HDD and a 128GB SSD.)

    Right now I have about 15% free space on the fusion drive. Is there an opinion on what the minimum free space should be on this setup?

  • I can create the Fusion drive using the 10.8.3 installer as described above. However, when i start the imac holding down the opt key, only the Mac os x installer (usb) drive is seen but the newly created Fusion drive is not seen at all! Please help

  • I’m afraid not, since any operation involving an array starts by recreating it. I may be wrong but I doubt it.

  • /dev/disk0
    0: GUID_partition_scheme *240.1 GB disk0
    1: EFI EFI 209.7 MB disk0s1
    2: Apple_CoreStorage 239.7 GB disk0s2
    3: Apple_Boot Boot OS X 134.2 MB disk0s3
    0: GUID_partition_scheme *1.0 TB disk1
    1: EFI EFI 209.7 MB disk1s1
    2: Apple_CoreStorage 999.3 GB disk1s2
    3: Apple_Boot Recovery HD 650.1 MB disk1s3
    0: Apple_HFS Fusion HD *1.2 TB disk2
    Logical Volume on disk0s2, disk1s2
    0: GUID_partition_scheme *2.0 TB disk3
    1: EFI EFI 209.7 MB disk3s1
    2: Apple_HFS Time Machine 1.0 TB disk3s2
    3: Apple_HFS External Disk 999.7 GB disk3s3

  • Hi, I created my custom Fusion drive with a 240gb SSD and a 1TB HDD on my 2010 iMac (had to remove the DVD drive and buy a mount for the SSD).

    The fusion drive works as advertised except one major problem.

    When I restart my system, the SSD is not recognized, and I get a questionmark on startup. I have to shut down my computer and press alt/option when booting to seletct my fusion drive to boot from and the it works. One note here, when I select the fusion drive, I actually see two fusion drive icons on the selection screen and I have to choose the first one.

    Please advise, thank you. I cannot “restart” my computer, I always have to shut it down and then switch it on with alt/option pressed. I worry that this is gonna wear my system down quite a bit.

    • @Alan,
      It’s possible that you haven’t “Set Startup Disk” in your system preferences since creating your fusion drive. Try that and see if it helps.

      • Thanks for the suggestion, but it didn’t help. I think the problem might be that the Fusion HD drive is shown as duplicate even when I restart the iMac and hold alt/option to choose the boot disc. If I then choose the wrong disc, then I get the same questionmark I get when I let the imac boot normally. It chooses the wrong of the two Fusion HD drives

    • This is a strange issue. It sounds like the PRAM is corrupted and resetting it should allow the startup drive to be proper set to the Fusion drive.

      PRAM Reset:
      1) Start the machine while holding down the Option-Command-P-R keys

      2) Wait until you hear the 3rd startup chime, then let go of the keys and let the machine boot up.

      • Hi Ben, unfortunately the PRAM SMC reset did not help…always the same. However another problem started to occur, when I leave the iMac without any activity, when the sleep mode occurs, the screen goes blank and I cannot “wake up” the iMac anymore, I have to do a hard reset to get the screen working :/

        So, I’m stuck with having to always shut down my iMac and I cannot “restart” my iMac because then, the “right” FUSION HD drive does not appear…this is very sad for me, since I am really enjoying the additional life the SSD brought to my elderly iMac (2010).

        I might have to take it for maintenance and maybe switch the harddisks so the SSD goes in pplace of the HDD and the HDD will be switched to the DVD drive empty connector (now it’s reverse).

        • Before taking the computer in for any service work, I’d recommend to break the Fusion drive and use the SSD and HDD separately to see if one of the drives appears to be at fault. If both drives work fine by themselves, I’d try to recreate the Fusion drive.

          It is possible the Fusion setup did not work proper. Breaking the fusion and reconfiguring it could be all it takes to resolve the issue.

    • Hi, would you send us the output of the diskutil list and diskutil info /dev/diskx where x is the number of the logical array (the fusion drive itself) ?

      • s1m0neiMac:~ Magneto$ diskutil info /dev/disk2
        Device Identifier: disk2
        Device Node: /dev/disk2
        Part of Whole: disk2
        Device / Media Name: Fusion HD

        Volume Name: Fusion HD

        Mounted: Yes
        Mount Point: /

        File System Personality: Journaled HFS+
        Type (Bundle): hfs
        Name (User Visible): Mac OS Extended (Journaled)
        Journal: Journal size 98304 KB at offset 0x240e000
        Owners: Enabled

        Content (IOContent): Apple_HFS
        OS Can Be Installed: Yes
        Recovery Disk: disk1s3
        Media Type: Generic
        Protocol: SATA
        SMART Status: Not Supported
        Volume UUID: 1D6D94B2-147A-33C7-8D2F-176C006FF690
        Disk / Partition UUID: 11162085-4EF9-46BE-BB1D-FDDCA3571EA3

        Total Size: 1.2 TB (1238420815872 Bytes) (exactly 2418790656 512-Byte-Units)
        Volume Free Space: 336.8 GB (336829689856 Bytes) (exactly 657870488 512-Byte-Units)
        Device Block Size: 512 Bytes
        Allocation Block Size: 4096 Bytes

        Read-Only Media: No
        Read-Only Volume: No
        Ejectable: No

        Whole: Yes
        Internal: Yes
        Solid State: Yes
        OS 9 Drivers: No
        Low Level Format: Not supported

        This disk is a Core Storage Logical Volume (LV). Core Storage Information:
        LV UUID: 11162085-4EF9-46BE-BB1D-FDDCA3571EA3
        LVF UUID: 1AFA233D-EC8A-4226-AF08-B43AC6EBDE52
        LVG UUID: 05B706AD-80D7-4A61-A3D4-282C5E504F71
        Fusion Drive: No
        Encrypted: No

        • That’s what I thought : your Fusion Drive is not correctly configured, look at the end of the output : Fusion Drive: No

          I guess you should try again following carefully the instruction provided by macasales. They should work for you as they are for me.

          Good luck !

          • Isn’t there any way to “repair” it without having to wipe my drive, create FD from scratch and restoring from TimeMachine?

            • “Isn’t there any way to “repair” it without having to wipe my drive, create FD from scratch and restoring from TimeMachine?”

              No. Converting a drive to Fusion is a destructive process. There’s no way to do it and preserve the data on it during the transformation.

              • Ok I de-fused and again re-fused the drive, this time I went through all the steps and did everything this guide described, but it did not solve my problem.

                After I fused my drives, I immediately restored from my ™ backup and after the first restart, the FusionHD drive showed up correctly (alt/option), however, the questionmark appeared again.

                I had to manually shut down my iMac and hold atl/option and then select the fist FusionHD drive from the selection (there was a second FusionHD drive too, the same as before), and everything booted normally. I checked the Fusiondrive from terminal using the command “diskutil info /dev/disk2” and it showed up Fusion as “ON”.

                What do you thing the problem might be? Is it possible that I might have to switch the disks so that the HDD goes in place of the DVD and the SSD in place of the HDD?

                Here is the result from diskutil:

                #: TYPE NAME SIZE IDENTIFIER
                0: GUID_partition_scheme *240.1 GB disk0
                1: EFI EFI 209.7 MB disk0s1
                2: Apple_CoreStorage 239.7 GB disk0s2
                3: Apple_Boot Boot OS X 134.2 MB disk0s3
                #: TYPE NAME SIZE IDENTIFIER
                0: GUID_partition_scheme *1.0 TB disk1
                1: EFI EFI 209.7 MB disk1s1
                2: Apple_CoreStorage 999.3 GB disk1s2
                3: Apple_Boot Recovery HD 650.1 MB disk1s3
                #: TYPE NAME SIZE IDENTIFIER
                0: Apple_HFS Fusion HD *1.2 TB disk2
                Logical Volume on disk1s2, disk0s2
                Unencrypted Fusion Drive
                #: TYPE NAME SIZE IDENTIFIER
                0: GUID_partition_scheme *32.0 GB disk3
                1: EFI EFI 209.7 MB disk3s1
                2: Apple_HFS USB 32GB 17.7 GB disk3s2
                3: Apple_HFS Install OS X Yosemite 9.0 GB disk3s3
                4: Apple_HFS DiskWarrior Recovery 4.7 GB disk3s4
                #: TYPE NAME SIZE IDENTIFIER
                0: GUID_partition_scheme *2.0 TB disk4
                1: EFI EFI 209.7 MB disk4s1
                2: Apple_HFS Time Machine 1.0 TB disk4s2
                3: Apple_HFS External Disk 999.7 GB disk4s3”

  • OK, I’ve added an SSD to my iMac from mid-2010. The original HD is a 1TB and it is backed up via Time Machine to my Time Capsule and a 1 TB USB drive. My current computer has roughly 700 GB of information on it. For planning purposes, after I create my fusion drive, how long will it take to restore my backup via Time Machine (planning on using the backup on the USB drive)? I’m assuming this is going to take a long time. Are there any power settings that I should set (not sure if the iMac will go to sleep during a restore or not). Thanks ahead of time!

    • 700GB of data over USB 2.0 can take about 4-7 hours. It is a variable transfer speed so it can vary quite a bit with that much data.

      As long as the file transfer is active the computer will not go into a deep sleep, the display might sleep which is fine.

  • You can actually determine if a coreStorage volume is Fusion or not, by running: diskutil cs info

    After extensive testing I didn’t find it improved performance after filling the SSD. Sure enough, the info command shows ‘Fusion Drive: No’.

    Any ideas on how to enable Fusion on a cs volume with Yosemite?

    • When I run diskutil cs info on Yosemite I get: Usage: diskutil coreStorage info[rmation] [-plist]
      Show properties of a CoreStorage object. A UUID or a disk can be supplied.
      ‘Not sure what it means… .

    • I too have this issue. Mid 2010 iMac with an original ssd and hd. I’ve followed the steps carefully but when I diskutil cs info the line about “Fusion” says Fusion: No.
      So I think I’ve created a core storage logical volume but it won’t manage data appropridately between ssd and traditional hd.
      Any ideas on how to fix this?

  • Last year I made my own Fusion iMac and worked great gor a few months. I went on vacation for the last two months and when I returned the mac had “unfusioned” when booting it would not see the hard drives. When I used Disk utility, it showed the SSD but not the Fusion drive, so I ordered a new HD and might as well a larger
    SSD, it installed them today following the instructions, but when I tried to start the computer, it gives the chime , and then a blank screen, I even tried some externals and they are not recognized either.

    Thanks for any tips


    • If I understand correctly the original drives used for the Fusion have been completely removed and installed a new SSD and HDD in its place. If the computer is not making it to the recovery partition, it may be something wrong with the computer, particularly the HDD drive spot. I’d begin by removing the HDD and see if that allows the computer to boot into the recovery. If it does, test the new HDD in an external to make sure it does not have any faults.

      • You are correct Ben, I ordered from OWC a 1 Terabit Toshiba and one 240Gig Mercury Electra to replace the existing ones, I reformatted them before installing them, and Disc Utility did not report any anomalies. Depending on how industrious I fell this week end, I’ll disconnect the HD and try again.

        Thanks again for your answers.

  • The thing I can’t find any information on is this: I have a 1TB Apple Fusion Drive (made by HGST), but I’ve put it in my 2012 MacBook Pro. Now I just want to make sure it is functioning properly or format it to be a Fusion Drive. Can you offer any advice on this? No interest in making my own DIY Fusion Drive.

    • If what you installed was a single physical drive from HGST then what you have is a hybrid drive and not an Apple Fusion. A hybrid drive has both solid state and disk drive in one shell and has its own software to combine the two so the computer sees it as a single unit. Because of this, you can treat it like a normal drive for the purposes of formatting it and using it.

      An Apple Fusion is actually two drives, an SSD and a hard drive. Fusion drives are two separate drives, an SSD and a disk drive, that are managed together by the Mac OS software.

  • As pointed out by Guy last year (bottom of this page), it is very important to type your SSD disk number before your HDD disk number! Type “diskutil cs create Fusion disk1 disk0” if your SSD is disk1 and your HDD is disk0. Otherwise only your HDD will be used (until it fills up then the SSD will be used). Apparently CoreStorage doesn’t determine which drive ‘appears’ to be the SSD. I made this mistake and only my HDD is in use.

    • I am getting ready to install a SSD in my 2012 macBook Pro (Today!).
      It was my understanding that I needed to replace the HD with the SSD and move the HD to the optical bay or I would be in the situation you found yourself in. What I hear you saying is that I don’t need to do that, I can simply specify the SSD first when creating the fusion. Have you confirmed this is the case?
      Thanks for your reply.

  • hello , I see the creation of core storage but where is the automated manager you referred to that manages fusion in you setup process. I do not see any difference here then other post on the internet.

    • The automated manager is built in with Corestorage technology. The 4GB buffer on the SSD is maintained, however whether smart migration of frequently and infrequently used data between the SSD and HDD occurs is so far not proven

    • Exactly my question. How can I make sure I am using an up-to-date disk utility that would perform automated storage tiering? I basically followed the steps above to create a “fusion” drive but now find that all subsequent writes all goes to the HDD instead of SSD, when the SSD is fully filled.

      Btw, I think it’s good to warn folks with 2009 macbook pro that this version of macbook pro does not work well with SSD with sanforce SSD controller, such as the Intel 530 that I’ve got. It would connect only at SAS-I speed…

  • One more question before I get started… I’ve read doing a clean install of Mavericks can be a problem if installer can’t create the recovery partition because of “something funky you have done with partitions”

    If I create a fusion drive on my MBP 17″ internal SSD (currently my main boot drive) and a partition on my internal HDD will it still leave the recovery boot drive partition on the SSD/HDD. If I clean install Mavericks on the new fusion drive is it going to be able to create the recovery boot partition if it doesn’t find one there?

    To be honest I’m in two minds as to whether I do a clean install or I do a standard migration from my CArbon Copy/Time Machine backups. Any ideas? I have 18GB of gmail data in Mail I would love to lighten off…

    • A core storage partition can’t be resized after it is created, so this prevents the installer from creating the recovery partition after you’ve enrolled the entire disk (ex., disk1) in CoreStorage.

      If you create the recovery partition first, then you can just the data partition (ex., disk1s2) into CoreStorage and then into your fusion drive.

      • Even though I just used the drive identifiers not the partitions it seems to have left a boot partition on both the SSD and HDD. Will see when I get through this. Just creating the logical “Volume” step ATM.

  • If I follow the procedure outlined here with Maverick, will I have a recovery partition automatically created?

  • Help! I’ve tried this on my Mac mini 2012 with Mavericks, and when I get to Step 13 I get an error (in Terminal):
    newfs_hfs: WriteBuffer: pwrite(3, 0x105fd2000, 1048576, 0): Input/output error
    newfs_hfs: write (sector 0): Invalid argument
    Mounting disk
    Could not mount disk16 with name (null) after erase
    Error: -69832: File system formatter failed

    I noticed at Step 10 I had similar disk0 disk1 etc. stats, but it went up to disk17 – lots of NAME untitled

    Why do I have so many drives listed?

    I have installed a Samsung 250GB 840 EVO as my SSD (internally), and using the standard 1TB platter drive in the mini.

    My boot drive is a USB.


    • What Steve said (minus his I/O error).

      I installed by Data Doubler tonight, expecting this would be a cakewalk. I have backups up the wazoo, so I’m not in a panic, but I simply can’t make this work. I get:

      diskutil coreStorage createVolume B8300DFC-E36B-4ECC-90C1-64C43AF56CA8 jhfs+ Macs 612.5G
      Started CoreStorage operation
      Error: -69720: There is not enough free space in the Core Storage Logical Volume Group for this operation
      $ diskutil coreStorage createVolume B8300DFC-E36B-4ECC-90C1-64C43AF56CA8 jhfs+ NEWDRIVE 612G
      Started CoreStorage operation
      Waiting for Logical Volume to appear
      Formatting file system for Logical Volume
      newfs_hfs: write (sector 0): Invalid argument
      Mounting disk
      Could not mount disk3 with name (null) after erase
      Error: -69832: File system formatter failed

      I’ve done this three times, and gotten the same failure every time. I tried initializing the bare drives to empty HFS+ volumes, then initializing them to Free Space, and neither one made a difference.

      If I try verifying or repairing the Fusion drive in Disk Utility, I get three quick overlapping “This drive is unreadable, initialize, ignore, whatever?” and DU fails before I can hit “Initialize” three times.

      I’m running 10.8.5 on a 15″ MacBook Pro mid-2010, using a 120GB SSD and the 500GB HD the Mac came with.

    • The list of drives will include externals as well. You’ll want to power down or unplug any external drives you have connected to your computer.

      To further clarify which drives are which you can find out within Disk Utility by clicking on the top of the drive (not the indented volume) and selecting Info in the tool bar. It will list the Disk Identifier there as reference.

    • To follow up my plea for help above – the errors I received were due to a faulty SATA flex data cable for the second drive. I originally purchased a cheap kit on ebay, and had the formatter error I described above. After replacing the cable with one purchased from PowerbookMedic.com, I retried and it worked straight away.

  • Hey All- I’ve commented here before. I installed a fusion drive in my 2011 MacBook Pro using a 240GB OWC Mercury Electra 3G SSD. For the most part- it’s amazing. But two things:

    1. The battery performance has decreased substantially since the fusion setup
    2. The system crashes quite often, when it never used to before. I’d say since the fusion build in Nov., the system has crashed at least 15 times, probably more. Everything freezes, the rainbow wheel appears and all I can do is manually power the machine down.

    Any thoughts?

    • I too occasionally get a beach ball on Late ’08 MBP Fusion setup. It’s usually a sign that the system has slowed to an absolute crawl – I wait about 3-4 minute eternity and it disappears – back to normal.

  • Thanks for the guide! Based on it and [jollyjinx’s articles](http://jollyjinx.tumblr.com/post/34638496292/fusion-drive-on-older-macs-yes-since-apple-has), I made this script which I used to help me test that my DIY Fusion setup is working correctly: https://gist.github.com/11522980

    Basically, you have to fill the SSD with garbage files until they flow onto the HDD, then repeatedly access files from the HDD while watching disk activity. Eventually the HDD activity will stop and SSD activity will continue (or start), meaning the files have been effectively transferred.

    Also, I’m using Mavericks and the two Fused drives are both external drives.

    • You mentioned your fusion drives were external, and this is the first mention I have seen of that. I have a 4TB hd and a 1TB SSD and I was thinking of getting this thunderbolt dual drive dock and make an external Thunderbolt Fusion drive. Is the method any different than the internal drives?

  • Has anybody migrated a mid-2010 Intel iMac equipped with an Apple SSD + Apple HDD to a Fusion Drive config?

    I have a mid-2010 27″ Core i7 iMac with 16 Gb RAM. It came with a 256 Gb SSD that currently has OSX Mavericks and our user accounts, and a 2 TB HDD that has over time being used to extend our user accounts especially with video content.

    I am currently pondering if and how migrate this setup to a Fusion Drive environment in order to “unify” user accounts into a same logical volume and optimize performance.

    I have a dual Time Machine backup (both on a TimeCapsule and on a 4 TB USB disk) that currently reflects this dual drive architecture.

    I don’t know how to “convert” this setup into a Fusion Drive (would it be seen by the OS as a “true” one ?) and what would happen when “restoring” from such Time Machine backups into the Fusion Drive

    • Hi,

      I doubt that the fusion drive will perform much better than your hand made config. The aim I th fusion setup is making it transparent to the user.

      However, it is true that the 4go write buffer could possibly make your machine more responsive especially when writing to the disk.

      Regarding setting up the fusion drive, it’s as simple as following this guide and then restore your time machine backup. Osx will handle the rest.

  • I have this Fusion Drive running well on a Late ’08 MBP.
    Say on a Mid 2011 iMac I want to install a 256GB SSD in it and use this SSD for Maverick’s System and all Apps and Write to the Users Folders on the existing hard disk drive.
    Would Virtual Memory write to space on the SSD or would it page to the hard drive? (There would be over 100GB of free space on the SSD.)

  • I have an early 2009 quad-core Mac Pro, with a DIY Fusion drive running Mac OS 10.9.2, composed of an internal 3 TB magnetic HDD and an OWC Mercury Accelsior_E2 PCIe SSD that looks like a RAID controller to the system profiler. Other internal 1 TB magnetic HDDs have Mac OS 10.6.8 and Mac OS 10.8.4.

    I have booted the 10.8.4 drive with no evident ill effects on the Fusion drive.

    Can I safely boot the 10.6.8 drive? Once booted, can I safely copy files in either direction between the Fusion Drive and the other drives?

    • This isn’t something we have ever tested. The protocols to handle a Fusion drive were introduced in 10.8.3, so booting to anything later should be safe. Booting to 10.6.8, or anything pre-10.8.3, would be risky. If you wish to try it, it would be best to backup the whole computer and all drives installed to be safe. Most likely, though, it will damage the Fusion as 10.6.8 won’t know how to handle it; the Fusion drives are managed by Disk Utility, not by hardware.

  • First of all thanks for the great howto!

    I have built a fusion drive into my iMac (replaced the Superdrive) and everything works fast and like a charm. However I have problems backing the machine up with time machine. It always cancels the backup with an error. In the logs I can see lots of SrcErr:YES for various files. Always different ones. When I try to read the affected files I also get an read error, However after some time the same files seem work again.

    Any Idea or help what did go wrong here?


    • This error can mean a lot of different things. If you have an anti-virus on your Mac, you would want to disable it and see if the error continues to occur. Repair your Time Machine and Fusion drive with Disk Utility or DiskWarrior. Your OS installation may be corrupt as well, you may need to reinstall Mac OS onto your Fusion drive.

      • I have no anti-virus installed. I tried to repair the drive with disk utility, but still get the same error. I am a bit hesitant to reinstall the os, because I have no working backup…

  • Hi, I have recently installed and configured a DYI Fusion drive, using 240GB Kingston V300 SSDnow unit, installing it in place of the DVD drive in a 21″ iMac (2010).

    All went well hardware-wise. I followed a guide and set up a Fusion drive using terminal commands, preserving the recovery partition on the HDD portion of the logical drive.

    The problem is, everytime I reboot the system (Mavericks 10.9.3), the Logical drive is not recognized and I am greeted by a gray screen with a grey circle and with a diagonal line (means the drive was not detected, no system to boot).

    After that I shut down the system again (long press the power button), turn it on and the system boots without any problems.

    How could it be? What can be the problem? Should I have installed the SSD in palce of the HDD and connect the HDD the the DVD sata connection?

    Please help me, thank you!


    • It sounds like there isn’t a drive selected for startup. Go to System Preferences > Startup Disk. from there you should be able to choose the drive you want to use to boot the computer and on your next startup you shouldn’t see the “no” symbol anymore.

  • Do you need to enable TRIM with a 3rd party program after creating a fusion drive since the OS doenst support TRIM on non apple SSDs?

  • I wonder if you guys can offer any advice on my particular situation?

    I have a late 2012 21.5″ iMac. This particular computer has a single 1TB SATA HDD inside, and apparently the spot on the logic board for installing a second SATA drive is missing the connector. I would like to tear this computer apart and install 16GB of OWC RAM and a faster hard drive, but since current hybrid drives only have about 8GB of flash space, and since I am not yet willing to pay for a 1TB SDD, I thought I would try a different option. SanDisk recently released an Extreme Pro 128GB USB 3.0 flash drive with supposed read/write speeds of 260/240MB/s, respectively. So naturally I attempted to create a DIY fusion drive using the internal 1TB HDD and 128GB USB drive. The combination worked great at first with BlackMagic giving me approximately 200MB/s read/write speeds to the “Macintosh HD” drive. Unfortunately, in the last week my fusion drive has become extremely slow with beach balls all of the time. Now BlackMagic is giving me about 20MB/s read/write speeds. Before I trash this DIY fusion drive and go back to using the internal HDD, are there any suggestions on what I might try fixing? I have booted into the recovery partition and repaired disk permissions. The USB drive is the only drive attached to the computer. I am running the very latest version of Mavericks. By chance has the latest Mavericks update somehow damaged my DIY fusion drive? Has my external USB drive somehow failed? Any suggestions would be greatly appreciated.

    • I’m sorry to hear that your Fusion Drive has slowed down like that. If that is the SanDisk Extreme PRO USB 3.0 Flash Drive then the problem is in the flash drive itself. Thumb drive style external flash drives are intended for fairly basic, limited use. SSDs, while they also use flash memory, are intended to replace a hard drive outright. As such, they have extra features that a thumb drives do not, such as a different type of flash memory, wear leveling, etc. Without these technologies, and with the large amount of wear and tear that a Fusion Drive puts on the SSD portion of the Fusion, a thumb style flash drive will wear out very quickly. You always want to use a real solid state drive such as our OWC Mercury SSDs for setting up a fusion, and not a thumb style flash drive, memory card, or anything like that. Another thing to note is that while the Fusion setup will allow you to create an internal/external drive fusion, it is designed to work on internal drives only.

      • Thank you very much for the reply. So you think my 128GB Sandisk Extreme Pro died after about 14 days functioning as part of a fusion drive? I had read that Sandisk was using SSD controllers in these newest generation of USB drives, so I thought this particular USB stick might incorporate the same wear leveling found in a true SSD. I can tell you that it was very good while it lasted. For the first few days of use, I was getting around 200MB/s read/write which was considerably faster than the stock Apple 1TB HDD 60MB/s read/write. And this upgraded performance did not require any disassembly of the computer. So tell me this: If I open up the late 2012 iMac, is it possible to use perhaps something like a SATA III Y-cable to attach both an SSD and a HDD internally? Because although I have not yet opened up the computer, I understand there is only a single SATA plug on the logic board. Or maybe OWC will offer a hybrid drive of some sort that I can use to upgrade this computer? The current hybrid drives I have looked at seem to have a very, very small SSD portion. Also, do you guys now sell the adhesive that I need to seal this computer back up again? It is still under warranty for another 2 years, so if I open it up to swap out parts and then the logic board dies, it would be nice if I could seal it back up again such that Apple didn’t know I was inside.

        • I can offer an interesting update on my quest to speed up a base model late 2012 21.5″ iMac. I separated my DIY fusion drive and reinstalled Mavericks on the stock internal 5400rpm HDD. I am back to getting about 60MB/s read/write times which is expected. I took my Sandisk Extreme Pro USB and re-formatted it, only to get about 2 or 3MB/s read/write times. However reading a little bit more about SSD’s, I tried an experiment. After running “Secure Erase” writing zeros to the entire 128GB USB drive, the read/write performance is back to 240/260MB/s, respectively. So I loaded a separate version of Mavericks onto this external USB drive, and it runs extremely fast giving me the same 240/260MB/s read/write times when functioning as the boot drive. I believe this is because a fresh install of OSX is only filling up a small fraction of the available space on the drive, and before when functioning as a DIY fusion drive, the USB drive was completely full. I attempted to use the TRIM Enabler patch, but apparently OSX is not able to sent TRIM commands to external drives except through ThunderBolt. It therefore has come to my conclusion that this Sandisk Extreme Pro USB drive has either poor garbage collection or poor wear leveling characteristics, so I a going to attempt to “overprovision” the USB drive by formatting only 100GB of space (instead of the full 128GB) and recreating a fusion drive again. I will see if the performance degrades again. The extra unprovisioned space may allow whatever controller which is found inside the USB drive to do a better job. As a completely non-destructive way to speed up a stock iMac, the idea of using a very fast USB 3.0 stick as a boot drive makes sense. I found the Western Digital is now offering a single 2.5″ drive called the WD2 (squared) that combines a single 1TB HDD and a 128GB SDD into a single 2.5″ 9mm package. However the firmware inside the drive is apparently incompatible with OSX such that OSX can only access the 128GB SSD and the HDD goes unused. Perhaps this will change in the future. What’s nice about the OWC website is that anything you buy there has been tested to work correctly without any frustration or modification, and as of yet, neither the Sandisk Extreme Pro or the Western Digital WD2 drives are being listed on the website.

  • I’m on Mavericks and I’ve created a fusion drive with an external USB drive. I’ve tried doing a clean install and I’ve tried doing a CCC clone. if I do a clean install, the installer gives an error before the first reboot stage saying I should try again and leaves an error in the install log about drtool error -11. If I do a CCC clone, I can see the fusion drive in the Startup Disk prefpane and I can choose it, but the system won’t actually boot from it.

    Any ideas?

    • While you may configure a Fusion drive with an external drive it is not recommended. It can have sporadic issues such as what you’re experiencing. The best thing to try is delete the Fusion drive and recreate it. However overall we’d advise avoiding setting up a Fusion drive with an external enclosure.

      • I’m running that configuration (ssd + Firewire 800)for months without any problem. It’s stable, very fast and easy to configure. IMHO that’s the best solution for old macs having only one sata port. I
        definitely would recommend that.

        FYI it survived the wild unplug test.

    • Is it a “bootable” USB port ? Remember that any interface you install a fusion drive device on must be able to boot without third party drivers.

  • Early 2008 MBP.

    I am planning to replace the optical drive with my current HD and then put an OWC 240 GB SSD into the main bay.

    DiskDoubler bracket is not available for Early 2008 (non unibody) MBPs, but I found adapters which would make a connection possible.

    Those adapters have superdrive port in and a HD port/connector.

    So, with Mavericks can I now make my DIY fusion drive?

    • An early 2008 MacBook Pro has an IDE connection in the optical drive. We have only tested Fusion drive setup with SATA interfaces. The Fusion creation might work, we just haven’t tested it.

  • All the guides I’ve read say to combine both disks like this:

    diskutil cs create /dev/disk0 /dev/disk1

    but afterwards you will no longer have a recovery partition, since the whole drive is wiped. That’s pretty inconvenient for traveling machines like laptops, since you might not have a TM backup handy when you need it. The recovery partition is also needed for certain functions associated with FileVault2.

    I’ve seem some suggestions that the existing recovery partition can be left in place, instead of being wiped out, by specifying the data partition (instead of the whole disk) to be enrolled in core storage, like this:

    diskutil cs create /dev/disk0 /dev/disk1s2

    I’m interested to hear from others as to whether this has been tried, and how it is working for them.

    If this is a better way to do things, then I suggest OWC update their guide.

  • How do I undo this process ?

    • To delete a Fusion drive you will need to delete the CoreStorage logical volume group using 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”

  • Thanks for this awesome guide! I’m about to dive in but I have one question:
    If I set up the fusion drive with my HDD connected externally, and then move the drive to an internal slot (after using the optical drive to install bootcamp), will the disk ids change and mess up the fusion drive?

    • While we know Fusion drives can be setup with an external drive, we do not recommend it. We have not done the experiment you’ve outlined and while theoretically possible it would best to have the drives internally installed before setting up the Fusion. If that is not possible, I’d recommend keeping the drives independent until you can have them both internally installed.

      • Has anybody combined a SSD and HDD both housed in an external enclosure, say with thunderbolt connection? Even a 6G extreme with a less expensive but larger 3G drive might be interesting.

      • I get to step 13, the operation gets stuck at 30%. :( Any suggestions?

      • I run this setup (internal SSD, external HDD on FW800) for some weeks without *any* issue.
        The performances are really far better (at least for general familial use : music, video, basic pictures editing, media server) than a standalone HDD, even with a small SSD disk (60Go in my case). The OS is generally extremely responsive and will make my old imac last some more years.

    • I don’t think so, since the volumes is build around IDs.

  • I have an SSD installed and by existing HDD transferred with disk doubler. The HDD has three partitions on it. DO I need to remove these partitions first before making the Fusion drive.

    Also could I create the FUsion drive with just half the HHD and leave one partition as a separate ‘non-fused’ partition to put large files >4GB on? Desirable so these large files don’t interfere with Fusion drive operations, especially when recording video to large files like 100 GB.

    Also once I have a fusion drive is it possible to the partition it into smaller drives? Just asking b/c for organisational purposes I like having three drives but no big deal if I can’t.

    • It is possible to use a specific partition rather then the whole drive if you would like to do so. You’ll see the Identifier be specific for each partition, like disk0s2. I’d strongly recommend backing up all the partitions before attempting this just in case the fusion creation does not go properly.

      A Fusion drive cannot be partitioned.

  • Hi,
    Thanks a lot for this tutorial
    I did all the steps till the 13rd and everything worked well.
    Now I just cannot install Marevick. It says “The program OSX Maverick couldn’t be installed. It couldn’t be verified or is damaged”.
    What should I do? Can restore directly from my Time Machine drive or should I try to find another Mac and create a new Boot-USB?

    • The error makes it sound like your Maverick’s installer is corrupt or otherwise broken. If you have a time machine backup there will be a recovery partition on that. I’d advise to boot and restore from that.

      • Ok. I’m doing it.
        I’ll let you know if it worked.

        Thanks again

      • The restoration is done but my computer doesn’t start normally. It always shows the utilitarian windows like when I started on the boot-USB. When I press down the option key when turning on my Mac it doesn’t show the fusion drive but only the recovery drive.
        I have an early 2011 MacBook Pro.

        • This still sounds like a corrupted drive. I’d advise to delete the Fusion drive, as outlined in earlier comments, and start completely over with installing the OS and restoring your information.

          • I had this problem before, it turned out it is just a bad date/time config. (you unplugged the battery when installing the drives, then started the fusion steps right after that). You must somehow boot an OS for the “bios” to have an actual date/time (dated after the OS installer build was released), then install the OS with no problems.

  • Hi,

    Since I own a old iMac (early 2008), I can’t install two drives in it : there is only one SATA port and the chipset doesn’t support port multipliers.

    So I was thinking to use an external drive connected on the Firewire-800 port, knowing the risks that I encounter if there is something wrong with the external device.

    Is it technically possible ? You mentioned that FusionDrive is meant for internal drives.



    • I forgot to mention that I wanted to install an SSD drive internally of course :-)

    • Fusion drives can be setup with an external, however it is not recommended.

      • I have been trying to “roll my own” Fusion Drive on a mid-2011 iMac with Mavericks. I have an internal 500GB SSD as the boot disk and I planned to use a 1.0TB external HHD. Everything has gone well until I reach the point of creating the fusion drive and I get the message “Unable to unmount drive.”
        How can I get past this and create the fusion drive?
        I see you don’t recommend using external drives, is this because of the possibility of accidental disconnects?

        Thank you.

        • I’m sorry to hear about the trouble with the drive not unmounting. The way Fusion works, it doesn’t care if the drive is internal or external and will use any volume as part of the Fusion Drive. That said, it was designed to use only internal drives, so we advise against using external drives. As it isn’t designed to cope with the troubles an external drive can have, sudden disconnect being one of them, it can be caused to catastrophically fail if something happens to the external drive. With the extra components and vulnerabilities inherent in external drives, there is a good chance something can happen; if it does, the data is gone for good.

          As for your current issue, there are any number of things that can prevent an external, or internal, drive from unmounting. Usually it is a background process that is holding the drive, or something similar. On top of that, our testing has shown that creating Fusion Drives involving external drives are sporadic and unreliable at best.

  • I am generally happy with my DIY Fusion Drive as described in this blog on a Late ’08 MBP. (750GB HDD and a 128GB SSD in the optical drive.)

    My question is: as the drive is about 85% full (it was 92% full before cleaning up!), should I defrag it? Is defragging ok with this Fusion Drive (iDefrag Lite 3.3.2)

  • Hey Guys,

    Successfully installed the SSD and built a fusion in my 2011 MacBook Pro. Everything seems great except to things:

    1. I’ve had a few system crashes, probably 5 or 6. That’s more than I’ve had in the entire life of the machine. Any thoughts on this?

    2. The battery life has been severely diminished. Thoughts?


    • We are sorry to hear about the instability. The best thing to do is to try and isolate the issue to software or hardware. I’d advise erasing and reinstalling your OS and avoid migrating any data on to the drive at first. Test the computer to see if the battery life improves and if the crashes are gone. If the crashes still exist the next step is to break the fusion drive and try to isolate the issue to one of the drives installed. At that point it is best to contact our tech support

      • With reference to poor battery life after building the fusion drive: one possible explanation would be shifting content between the SSD and HDD portions, based on your usage pattern, especially after restoring user data and older software. I would expect that with a smaller SSD, or large files (e.g., VMware Fusion or Parallels virtual machines), it might take a while to stabilize.

  • So if I get 2 x 120GB SSD and 2 x 1TB hard drive, can I setup 2 seperate fusion drives and use RAID 1 via OS X to mirror the 1st Fusion to the 2nd Fusion?

    • Theoretically yes. However it wouldn’t be advised. For RAID functionality to properly work the drives need to be the same make and model. A Fusion drive being made up of a SSD and a HDD can have varying performance. If one of the fusion drives ends up storing the data on the SSD and the other one stores the data on the HDD it could result in data corruption or RAID corruption.

      It would be better to just have a hourly backup of your Fusion drive.

  • Awesome post. I think I’m ready. I have an early 2011 13-inch MacBook Pro, model ID MacBookPro8,1 and I’m running OS X Lion 10.7.5. I’ve just received my data doubler kit w/240GB SSD. Anything I need to know or do differently since I’m jumping straight to Mavericks?


    • The process is the same for Mavericks, nothing has changed. We hope you enjoy your new SSD and Data Doubler!

      • Hi Ben-

        Welp, my Dad and I have installed Mavericks on my mid 2011 13-inch MacBook Pro, we’ve installed the data doubler and SSD, etc. But we’re getting stuck on Step 8 – Boot to the newly created 10.8.3 Installer.

        When I try to boot to the external (pressing option), I get two options: my original internal HD and a disk that says “Recovery 10.9”, but nothing else. When I select the “Recovery 10.9” and try to do steps 9 through 11, I get a 69888 error message (unable to unmount disk). I think that’s because I’m not actually booting to the external.

        Any thoughts? I can send pics of the terminal messages, if need be.

        • Ken, it does sound like your machine is booting to the internal recovery partition. The 10.9 installer that was made must not be working, you can try to recreate it or better yet if you have a time machine drive you can boot from the recovery partition on that.

  • Hello OWC,

    I have made the Fusion drive in my iMac 2011 27″ (12,2) with 240 GB OWC Electra 6G SSD + original 1 TB HDD. After the creating the Fusion array I made clean Mavericks installation. Everything was fine but then the OS X has frozen (with “rainbow circle rolling”) and I had to power it down manually by pressing the power button. It seems it freezes when open certain app – sometimes its a Safari, sometimes Preferences etc. Sometimes the iMac freezes after first app after boot is opened, other time after while (15 minutes). I have also turned off the “HDD sleep mode” as I thought it could be the issue. But it was not.

    I have disk0 = HDD and disk1 = SSD… so I typed the command opposite as faster disk has to be the first in the order, otherwise the Fusion is not working at all.

    diskutil cs create fusion disk1 disk0

    Should I plugged the SSD and HDD opposite on the logic board in order to have the SSD as “disk0”?
    Before making the Fusion I updated the SSD with the new firmware succesfully.

    Please could you advise? Have you experienced thi issue?

    Thank you for any help in advance.

    • This is an odd issue. I would advise breaking the fusion drive at this point and installing the OS on just the SSD to see if you experience the similar issue on the SSD. If the issue persists on the SSD, you’ll want to get contact our tech support

      • Hi Ben,

        thanks for reply. OK, I will tray to destroy CoreStorage and install the Maverics to SSD. If the problem persist on SSD itself I will contact tech support.

        • I would first try and run a surface scan on the volume (even if the 1tb hard disk is a brand new one, it might have bad sectors already). It’s ok to run this test in the same volume as the SSD since the SSD would not show any bad sectors. I would recommend using TechTool Pro or similar app to run the surface scan, but I am unaware of any good free ones.

  • Hey guys.

    tomorrow i’m gonna get my SSD to build the Fusion Drive.

    But there’s one thing i want to clearify before doing the “big” work.

    My plan is to Build the Fusion Drive (HDD [500gb into optical bay], SSD [250 gb into main bay]).
    I already did 2 Time-Maschine Backups on 2 different external devices.

    And now the thing i’m worried about:
    When i create the Fusion-Drive, all 2 HD’s are erased, right?
    So when i’m doing the clean install of Mavericks im wondering, if the Recovery HD (latest version) is created too?
    Otherwise i’ll have to create it manually BEFORE doing the Fusion?!

    (System: MBP late 2011, 500 gb HDD, 8 gb ram, Lion 10.7.5)

    Best Regards,

    • You only need to worry about the recovery partition when cloning (and even then, as long as you use CCC or SuperDuper you’ll be fine). Just install mavericks and then use migration assistant and you’ll be good! Also, I put my HDD in the original spot for the sudden motion sensor.

      • Thx for your fast replay!

        I read a lot about where to put the SSD.

        My MBP says: on each SATA Link i got 6 GBit.
        Right now HDD (negotiated Link-Speed 3 GBit)
        Optical Drice (negotiated Link-Speed 1,5 GBit)

        So, where should i put my SSD and my HDD?

        I checked my EFI: 2.7

        So is the SSD in the Optical Bay still unstable?



        • I don’t know about “unstable”. I think it’s more what works for you. With my SSD in the mail bay, I could only negotiate a link speed of 1.5 but with it in the optical bay, I can usually get 3 (and shutting down and restarting us usually fixes this if now). I have an 09 MBP and this is a known issue. If you get 3 Gbps, that’s good.

          FYI, you can swap you SDD and HDD placement and the Mac still boots fine.

          • Hi,

            FusionDrive successful built BUT the installtion from the USB-Stick doesn’t work. I always get a message like: “The Programm OSX Mavericks couldn’t be installed. It couldn’t be verifyed or is damaged”.

            I got the FRESH Mavericks from the App-Store! -> Did the Terminal way for the Boot-USB.


            • Interesting. I used the “Lion Diskmaker” app to make mine and it worked fine. Do you have another Mac or a friend with one you could use to remake your boot USB?

              • Problem got solved!

                That’s the way i did it:

                1. Created Fusion Drive
                2. Created a Mountain Lion 10.8.4 (with Fusion Drive Drivers) on a second Boot-USB on my iMac
                3. Installed 10.8.4 on the Fusion Drive (it worked!!) with Boot USB
                4. Formated the Fusion Drive
                5. Installed 10.9 onthe Fusion Drive with the second Boot USB Stick.

                Perhaps a problem with the Update from Lion2Mavericks?!?

                By now, my MBP runs @ Fullspeed :)

                Thx Colin for every help!


    • When you create a fusion drive the two drives being used will be erased. A recovery partition cannot be created on a fusion drive either. If you have a time machine backup you will have a recovery partition on that drive.

  • Very well written.
    Worked first try for my old 2009 MBP 15. Wanted to have it run like than for more than a year now.
    Even learned a little to understand writing in Terminal.

  • Cloning is not recommended as a way of installing onto a DIY fusion drive. (This is maybe because the cloning software is missing something when it comes to DIY fusion drives?)

    Is cloning as a way of installing onto a rebuilt DIY fusion drive still not recommended when the clone is of an earlier functioning fusion (Mavericks) setup?

  • Great post! Thank you for all of that essential info.

    One extra point: When you create the logical volume group, you must specify the faster drive first (e.g. “diskutil cs create Fusion disk1 disk0” if disk1 is the faster drive). Otherwise CoreStorage just fills up the slow one first! I learned this the hard way, by listening to my HDD working when it should have been the SSD, but you can also check using the iostat command as shown here:

    Now that I’ve fixed that, the fusion drive is working beautifully! Thanks again.

    • Great tip! I’ve never heard that before but it would be really important. Are you using an optibay with a MacBook? If so, do you have any issues with the SSD being the the optibay and not the original HDD spot? I’ve heard that the SSD should go in the normal SSD spot but then you lose drop protection on your HDD which is less than ideal.

      • On my MacBook, I put the SSD in the optical drive bay and have never had a problem with the function. I am confined to Sata II in both drive locations, so this works fine.

      • I was working on a 24″ iMac and replaced the DVD drive with an SSD. The hardware part of the process is described in a fine iFixit tutorial and worked like a charm. The only problem was in the creation of the fusion drive, but now that everything is working the iMac is better than new.

        I don’t have any info about the drop protection – sorry.

    • Good point. So, how did you reverse the order? Dis you go through the whole process over? Or, as a newbie, is there something I don’t know?

    • Thank you Guy! I made the exact same mistake you described. I have just discovered it because I noticed the iostat command output is showing only my 4TB HDD in use and my SSD has never been touched.

      I started to think that the HDD being indexed first in the CoreStorage LVG (logical volume group) was the problem. I looked all around and found no article that points this out until I found this post.

      I will start all over and redo it, I can probably spend less than a half day this time with the TimeMachine migration too.

  • Hello everyone,
    Hello OWC Team,

    First, thanks for this tuto ! It works like a charm !

    In october, I purchased a Mac mini late-2012, i7 2.6Ghz, 4GB RAM,1TB 5400rpm HDD and planned to boost it with a OWC 8GB RAM chip (Total 10GB) and the OWC Mercury Extreme Pro 6G 120GB SSD !
    Because it was a brand new device, I booted it up first , then run some tests to see if everything works perfect ! So if it wasn’t working after my “Boost Operation” I would be the guilty.
    So, I follow the current OWC guide and succeeded easily.
    The mac came with Mountain Lion 10.8.2. as far I can remember. But I had a copy of Mavericks installer. I made a FireWire boot disk from it, following this guide : http://www.coolestguidesontheplanet.com/making-a-boot-usb-disk-of-osx-10-9-mavericks/

    After creating the Fusion Drive from Mavericks installer (Terminal), the installation went smoothly. I noticed 2 BIG steps of Mavericks installation longing like 30-40 minutes each. Then you’re done !

    Hope my testimony will help some of you.
    Good luck.
    (Sorry for my english, Frenchie inside)

  • I was successful in installing a ssd into my mac mini late 2012 and creating a fusion drive from scratch on Mavericks.. All new to me! Thanks for the guide! I had sweaty palms throughout the whole thing!