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.


  • This may already have been addressed, but:
    I have a Mac Pro (2010 Quad-Core) equipped with 4 WD VelociRaptor (WD1000DHTZ). Would I REALLY see any noticeable improvement with a Fusion drive?
    If so, how many HD’s can I include? Am I limited to just 1 SSD and 1 HD?
    I have a love/hate with my MP. I need speed, but I also need space.
    Any advice?

    • Setting up a Fusion drive is only possible to do with a single SSD and HDD. Fusion drives are a very nice upgrade for consumers and select prosumers. It is our recommendation for BEST performance to manually manage your data between SSDs and HDDS. Fusion gives users zero control over which information is on the fast SSD and the slower HDD.

      If you need speed and large amounts of storage you can look into creating a RAID 0 using Disk Utility

  • I will be attempting the DIY Fusion Drive on a 24″ 2.93 GHz Intel Core 2 Duo 2009 iMac with an OWC data doubler and 240GB SSD. I wont be doing the drive install myself (not that im not technically inclined, just simply wont to take any risks). I am hoping to find a solution for breaking the Fusion Drive once created, just incase I’m not a fan of the results, without having to remove the drives again. I read the earlier comment on how to separate the drives after, I’m just wondering if anyone has discovered a safe way to do this without cracking open the machine again and removing/reinstalling the drives.

  • I am attempting a Fusion drive setup on a system that technically can’t run Mountain Lion per Apple’s system requirements (Late 2007 MacBook). I’m installing ML by way of MLPostFactor:


    I have an SSD installed in the main hard drive bay, and replaced my old SuperDrive with a HDD. It’s a setup I had been using well for over a year…running Lion and my usual apps off the SSD, and most of my home folder and other apps/files off the HDD. But I have been intrigued by the progress made with getting Mountain Lion to run on older systems, so I thought I’d give it a shot and get a true Fusion drive setup in place as well.

    Needless to say, I’ve run into a major stumbling block. I can get up to step #13 above, but when I try to format the volume, the progress bar stops at 80% and the system kernel panics. Upon rebooting, the disks show in Disk Utility as being fused, but the volume created is unmounted and shows as essentially being full, so I can’t install ML on it.

    Disk Utility is the proper version (13 (444)), and I am using the proper Terminal commands, so I am at a loss as to why it’s not working. I know this is an unsupported setup, but another user on the MacRumors forums managed to do something similar on his 2006 MacBook Pro so I gotta think it’s still somewhat doable. Any thoughts as to why it might be freezing up on me?

    Photo of lockup…


    • I have exactly the same ERROR (on 80% fusion drive creating) on MlPostFactor 0.3 and 10.8.4, can anybody HELP PLS???

    • Dear friend, have U resolve it?
      I have tried 10.8, 10.8.4, mlpostfactor 0.2.2, 0.3 – all the time @HALT@ on 80%.
      White MacBook 2007 Late.

    • I resolve it!!! (by use my iMac)
      1.diskutil cs create Fusion disk0 disk1
      2.diskutil coreStorage createVolume UUID jhfs+ “Macintosh Fusion” 100%
      3.ERROR at 80% -> power off macbook
      4.Connect to iMac by use of firewire cable, power on macbook with press “T” (Target Disk Mode)
      5.launch “Disk Utiliy” in iMac, Just format MacBook’s Fusion disk!!!
      6.Install MLpostfactor!!


  • I successfully setup a Fusion drive with a 240mb flash drive from OWC and a 750 GB Seagate drive with a data doubler bracket in the optical bay. It runs fine as a single drive, but now the fan runs constantly. Is there a fix for this?

    • It sounds as if a thermal sensor was not plugged back in when performing the install – if it isn’t receiving data, it assumes the sensor has overheated and runs the fans to cool it down.
      For further troubleshooting, please feel free to contact our Technical Support Department at 1(800)275-4576, via email or live chat.

      • Just wondering if a 7200 rpm drive is too much for the MBP. Perhaps a lower rpm drive would run cooler?

        • It really shouldn’t be – before SSDs, the first upgrade I made in every laptop I used was to change out the 4200RPM or 5400RPM drive for a 7200RPM drive in a larger capacity. Never had an issue with overheating.

  • when I run the “diskutil cs create Fusion disk0 disk1”, command I get this error
    any ideas

    Started CoreStorage operation
    Unmounting disk0
    Repartitioning disk0
    Unmounting disk
    Creating the partition map
    Rediscovering disk0
    Adding disk0s2 to Logical Volume Group
    Unmounting disk1
    Repartitioning disk1
    Unmounting disk
    Creating the partition map
    Rediscovering disk1
    Error: 22: POSIX reports: Invalid argument

    • We did a bit of digging online and the POSIX error would seem to be an issue of how the drive is being addressed. The fix that was reported on a few different sites said to address the disk’s partition rather then just the disk. So use “diskxsy” Where x is the appropriate disk number and y is the primary drive partition.

  • I recently did a clean install where I redownloaded and reinstalled 10.8.3. Would I have the correct version of Disk Utility to skip steps 2 through 6, or would I still need to download 10.8.3 from the Mac App Store and put the install file on a usb drive?

  • Even after checking with numerous guides, every time I go to type in the “diskutil cs createVolume” command, it either gives me an error saying the logical volume cannot be rediscovered, or it just stays stuck on the percentage line. I’ve tried this several times and still get one of the two errors every time. Do you know what could possibly be the cause of this?

  • Hi!
    I need some help. Today I received my OWC data doubler and installed it in my late 2008 MacBook and everything was ok, until I needed to reinstall the mountain lion (“Step 14 – Close Terminal and Install OS X. Now that we have created the Fusion volume, 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”). The only problem is that I can’t choose the Fusion drive, because the only drive that appears is the USB flash drive that is with the Mountain Lion, and even this one I can’t choose, it says its protected. I went to disk utility and my fusion drive its there, but cannot change it because its says that it’s protect. Anyone one can help me with this? I just want to install the mountain lion and enjoy my fusion.

    • Vítor, we received all three copies of your comment, perhaps you missed the note at the bottom of the comment submission page:

      Please note that comment approval and/or replies to approved comments may take up to 72 business hours.
      If you require more immediate and specific technical support assistance to resolve a matter you are currently
      experiencing, we encourage you to contact our technical support department via:
      Live Chat
      or telephone at 1-800-275-4576 | 1-815-338-8685

      That said, the USB drive would be protected as you cannot reformat or reinstall an OS on the drive you’re booted to, but the Fusion once formatted should not be showing as protected in Disk Utility. It sounds a lot like steps 12 and 13 were either skipped or errored out somehow.
      Open Terminal and try those two steps again making sure that your terminal window states all the steps shown in the image after Step 13. If the drive didn’t format for some reason, then it won’t show up as a valid destination to install the OS.

  • Following this guide to create a DIY Fusion drive on a 2011 Mac mini worked great, but now I have two identical Macintosh HD disk icons listed on the boot screen (holding down Alt at startup). Both icons load OSX. A genuine Apple Fusion drive will only show a single Macintosh HD icon on the boot screen. Is there any way to hide one of these icons?

    • @Justin: I want to know that too! or at least what’s causing it…. it think there’s a boot partition on the second drive as well but is it necessary? Can that one be deleted?


      • While it seems easy to hide a drive or partition inside OSX, doing so in the EFI environment seems more problematic. I suspect that the mechanical hard drive portion of a “genuine” fusion drive might use a custom firmware that hides one of Macintosh HD icons in the boot screen. But maybe someone has a better idea?

    • Having two volumes from the Fusion drive show up on the boot selector screen is normal. There unfortunately is no way of hiding one of the volumes.

      • So how does Apple do that :o) Since there is a way to ‘break’ their Fusion Array also ending up with two drives.

        Is it really necessary to have an EFI partition on the second drive? Most of the time that’s what make a drive show up?
        Will partitioning the drive as Apple or MBR and not as GUID affect this?
        And if possible what’s the consequence for Bootcamp?

        • I also notice that on a genuine Apple Fusion drive, I can change the icon of the Macintosh HD logical volume in finder and then the new icon shows up on the boot screen, but on my DIY fusion drive, if I change the icon of the Macintosh HD logical volume in finder, on the boot screen I still get two of the standard Macintosh HD disk drive icons. I attempted to change the icon of only the SSD (comprising a part of my DIY fusion drive) so I could possibly identify which of the two Macintosh HD icons is which at boot, but once the volumes are fused together this appears to be impossible.

        • Apple unfortunately does not provide many details about the inner workings on their Fusion drives.

          Mac OS X will only install onto a GUID partition table, so partitioning the drive as MBR or APM is not recommended.

          When using boot camp on a Fusion drive the boot camp assistant will partition the HDD and leave the fusion partition alone.

          • Yeah!

            I found the cause and (NOT THOROUGHLY TESTED!) solution for deleting the double startup Drive with a DIY Fusion Drive.

            Startup from an external Drive

            Put DiskUtility in Debug mode by typing the following in Terminal:

            defaults write com.apple.DiskUtility DUDebugMenuEnabled 0

            And than tick/select:
            Show All Partitions

            in the DiskUtility Debug Menu you will see that the second drive (probably your old HDD) contains a part ion called:
            OS X Boot it was about 134MB big (small) on my HDD

            Under Partion DELETE that OS X boot partition (it’s useless anyway) because your never going to boot from that CoreStorage drive anyway.

            The second boot icon wil disappear from your ALT/Option boot menu, only the InternalHD-icon from your SSD wil show up.

            Although it works like charm on my mid 2010 iMac (i could do the test because it was empty anyway after Fusionizing it) I DID NOT TEST THIS WITH BOOT CAMP, so use at your own risk

            • Ooops, made mistake in Debug mode, it must (of course be:)

              defaults write com.apple.DiskUtility DUDebugMenuEnabled 1

              to enable debug mode voor DiskUtility

              in orde te be able to see and erase the small Boot OS X partition on your second drive.


              • This worked for me. However the OSX Boot portion on my HDD (disk1) was 650MB. I was not able to delete it in the partition menu, but instead was able to erase it in the format menu. It then appeared as a separate partition. When I went to the partition menu to try and erase it, I could not getting an error “this partition is too small to erase”. But when I exited out of DiskUtility and then reentered DiskUtility, that portion was gone. Maybe I lost 650MB of storage, but it is gone. Rebooting holding Alt now gives me just the Macintosh HD partition and the Windows HD partition (just like a genuine Apple Fusion drive). However I am still not able to change the Macintosh HD icon in the EFI boot screen. On a genuine Apple Fusion drive, changing the Macintosh HD icon in finder results also changes the icon in the EFI screen. But on the DIY fusion drive, this does not work. Any ideas?

  • Did this with a late 2008 unibody macbook (non-pro) and I am less than a genius. Used a Samsung 250gig ssd and wd scorpio blue 5400 rpm 640gig hdd. I failed to use “100%” as my drive size and lost 35gigs in the conversion probably going to redo all of this again (it was fun) as to regain lost space. I’m getting consistent write speeds of 200mb/s and read speeds at 350mb/s now I know this wont last forever but the update to my late 2008 uni is easily apparent… If you haven’t done this yet you are weird and need to be checked for disease :) thanks OWC AND WHOEVER you credited for the info!!!! All this only took me 1 1/2 including restore back to desktop…. Ohh yeah and I’m getting boot times at about 18 seconds!!!! Love this upgrade, comparable to going from iPhone 2g straight to iPhone 5 ;))

  • Today I created the Fusion Drive following the OWC guide exactly, using DiskUtily (13 build 444)
    After doing so I found out that my new Recovery Partition was unaccessible because it was located IN the LVG (the Fusion Array).

    On my iMac 2010

    Reinstalling ML 10.8.3 from USB did not help, the Recovery stayed in the LVG and was not accessible.

    I therefore guess/suggest it might be better to adapt your DIY Fusion Drive Guide, on step 11 and make another approach beforehand.

    I (think I) succeeded having a working Fusion Drive and an bootable Recovery partition (Command-R) by doing the following:

    1. Boot from the 10.8.3 USB (as described)
    2. wipe/repartitio the SSD (Disk0) and HDD(Disk1) using GUID and leaving only EFI and the 1 partition on both drives
    3. Install 10.8.3 on the SSD only (in my case Disk 0), thus forcing the Recovery Partition to be on Disk0, Disk 1 stays untouched.
    4. After the install (don’t waste to much time on it, it gets wiped again) reboot from the USB
    5. open Terminal to check if it indeed created a recovery part ion (about 650MB) on Disk0s3
    6. Use diskutil BUT NOT AS DESCRIBED in Step 11 of the guide.
    7. Instead use: diskutil cs create drivename Disk0s2 Disk1 (where Disk0s2 is the main partition of the SSD and Disk1 your HDD. This way you leave the Recovery HD (Disk0s3) intact.)
    8. Follow the guide from step 12
    9. Install 10.8.3 for real this time

    You are able to boot into Recovery now by pressing Command-R

    Only thing that’s ‘strange’ or at least not the way I like it to see:
    pressing command-option gives me two Fusion drives to start from and not just one and the Recovery 10.8.3 like I would like to/was used to.

    If anyone has a better suggestion to achieve this (to maintain recovery HD and have a DIY Fusion Drive) please reply.

    I ALSO wonder if this would be a great method to force the Windows partition to be on the SSD (and forget about Boot Camp 5. I guess prior to my step 6 you have to partition you SSD to (just add the last partition in Disk Utility):
    disk0s1 EFI
    disk0s2 HFS+
    disk0s3 Recovery
    disk0s4 FAT32/empty/NTFS

    Anyone tried that yet? (I personally think Boot Camp should let us decide where to place the Windows partition)

    Hope this helps…

  • I was thinking about using this setup on my base-model late 2011 MBP. Will this work with a Seagate 1TB SSHD in the hard drive bay and the OEM hard drive in a optical drive caddy? (Thus resulting in a 1.5TB Fusion config?)


    • Don’t see any reason why it wouldn’t.

    • Very interesting idea. I got the data doubler from OWC along with a 120 GB SSD and a 240 SSD and put them both in my mid 2009 Macbook Pro. Anyone have an idea whether I can create the Fusion drive with the two SSD’s in the MBP?
      Right now my startup disk is the 120 GB in the optical bay. Seems to be working fine after I tweaked the wake on sleep setting.

  • I just installed a OWC Electra 3G in my Late 2009 iMac. I removed the optical drive and installed the SSD then went through the steps listed above to create a Fusion drive (my other drive is a 2 TB Hitachi that came installed in the iMac). Now that i’m up and running again, applications and computer start up/shutdown seem noticeably faster. The only hiccup is that I ran a BlackMagic speed test on the Fusion and was disappointed with the results. 104 Write Speed and 162 Read speed….(MB/s) Is this normal?
    I just want to make sure that I haven’t made any mistakes.

    Thanks in advance for any help you can give.

    • BlackMagic uses incompressible data in its testing. On a SandForce-based drive, this would report lower speeds, since the Durawrite technology used in the Sandforce controller compresses data in part to achieve its speed. The BlackMagic test is good for a worst case scenario of write speeds. We’ve found that the QuickBench Speed Tools benchmark (which uses compressible data in its testing) shows more accurate speeds for the average user.

      BlackMagic does performance testing to help determine suitability/capability for various video-related functions. Raw video capture deals with compressible data… whereas conversion and editing of already compressed video file types is dealing with incompressible data. If the purpose of your benchmarking is for the optimization of a video production workstation, then BlackMagic would be the test to use – for most other purposes it isn’t going to give real-world results.

  • I have read with great interest this great post and all comments. Thanks everyone for all the great information.

    I also followed Jollyjinx’s instructions to create a “fusion drive”. In my case, I used a 256GB Samsung 840 PRO Series SSD drive and a 320GB WDC WD3200BEVT-11ZCT0 5400RPM hard drive.

    The original hard drive in my system was the 320GB WDC. It was ALREADY running 10.8.3.

    So, before I started, I backed up everything to an external 500GB WD Passport Studio USB drive, named Passport_500, by using SuperDuper. Then I removed the optical drive and installed OWC’s Data Doubler tray, moved the original 320 GB WDC hard drive to the tray, and installed the Samsung SSD on space left after I removed the original drive. Then I rebooted the system from the Passport_500 and created the “fusion drive” by following Jollyjinx’s instructions. Once the new 568,56 GB volume (which I named Macintosh HD) appeared, I restored the backup from Passport_500 to the new Macintosh HD. When the restore process ended, I shutdown the system, disconnected Passport_500 from the USB port and restarted the system, now from the new Macintosh HD.

    Everything worked fine and I immediately noticed the system was faster than ever. I’ve been using it for the last week without problems. After reading this post, I verified that “CFBundleShortVersionString” and “CFBundleVersion” from “version.plist” file inside the Disk Utility combo and they match 13 and 444 respectively.

    So here is my question: Does the above mean I have a “true” fusion drive?

    Thanks in advance.

  • Hi from France,
    First, thank you very much for a very interesting and technical post.
    I am actually running Snow Leopard on my iMac ( 10.6.8).
    Do you think it is possible to use some 1T and a 128 SSD installed in the same enclosure connected to my iMac with firewire to set up an external Fusion Drive running Mountain Lion ( I have 10.8.3 on my MacBook Pro) ?
    Could I then boot my iMac from this “external” Fusion drive ?
    I would like to do this for testing purposes, if it works nicely it would be like having 2 possibilities to start from : Snow Leopard from internal HD or Mountain Lion from external Fusion Drive ! Not to worry about datas.
    Thanks again

  • Hi Guys,

    Thank you for the detailed info. After reading this article I purchased a data doubler and a new Samsung 120GB SSD.

    I have two questions:

    1- Since I will make the disks a fusion drive installing which disk to which port does not matter much anymore right? I am thinking about putting SSD to the CD-Rom bay and keeping my classic disc in the usual HDD place for disc protection and lower noise. Please let me know if doing vice versa is better or this idea is the logical one.

    2- My classic disc is not really the most classic disk. I have a Seagate Momentus XT Solid State Hybrid disk. For the ones who dont know it is a SSD-Spinning Disc hybrid. It has 8GB internal SSD memory and the remaining 492GB is a usual 5400 RPM spinning disc. Momentus XT moves the files to/from the 8GB part automatically and it is something done in the hardware level rather than software and when I used “diskutil list” command disk appears as a one 500GB disk instead of different disks. My question is: Did anyone try this disk for fusion drive before? Do you think it would cause any problem for fusion setup? Or can I do it without any hesitation?

  • Very interesting article! I still have a doubt: is fusion purely software or do you need a specific hardware component? For hardware, the only thing I can see is: “A Mac that you can install both a Solid State Drive and a Hard Disk Drive into”. Is it the only constraint? Of course you need latest 10.8 version with latest disk utility so could imply also some other hardware requirements [according to Apple website: iMac (Mid 2007 or newer) / MacBook (Late 2008 Aluminum, or Early 2009 or newer) / MacBook Pro (Mid/Late 2007 or newer) / Xserve (Early 2009) / MacBook Air (Late 2008 or newer) / Mac mini (Early 2009 or newer) / Mac Pro (Early 2008 or newer)]. Actually I just wonder if Fusion is not something like real Intel® Smart Response Technology with some tweaks at the OS level. And if Apple is using Intel’s technology, would mean you need to have an Intel SRT capable chipset: Intel® Z68/Z77/H77/Q77 Express Chipset-based board + Intel® Core™ Processor in the LGA 1155 package according to Intel support webpage. Do you guys know?

    • The Mac that you can install OS 10.8.3 or later, a Solid State Drive and a Hard Disk Drive into is the only hardware requirement.

      • I have a question about the size of the SSD for DIY fusion drives. I’ve been reading a lot and have not seen anyone use a drive smaller than 128gb, while some use larger drives. Can I use a 64gb SSD? On the other end, will using a 256gb SSD give noticeably better performance than a 128gb? In a 256gb (or larger) SSD configuration, is there still only 4gb of write space?

        • Any size SSD can be used. The 4GB buffer size will be the same no matter how large the SSD is.

          Storage capacity of the SSD generally does not affect performance of the drive as much as Hard Drive size matters. Due to NAND Flash configurations the 240-256GB SSD capacities are generally the fastest SSDs.

  • Well I ordered my OWC 120 gb electra 3G SSD and Data doubler for imac/macmini ….. installed in iMac 27″ 2009 late model which has a stock 1TB WD drive …
    Followed your instructions on how-to build a DIY Fusion drv and now running top form .. loving it ……
    Boot time is so fast now apps are snappier .. list goes on …..
    thks for the info … cheers Don

    • @don Howell What speed are you getting from the SSD? I ran black magic to get a speed test of sorts and got SE very unsurprising numbers. (Also using late 2009 imac with Mercury Electra 3G and a 2TB Hitachi fused together…

      • My speeds are great it’s been over a month now and lots of use and is still as fast as when fusion was first created
        Using Blackmagic disktester will show numbers for worst case video codecs. I have tested can’t remember what they were but much faster than HDD
        I have SSD’s in my MBP and MacMini which are fast the MBP with 6G intel chip has a owc extreme pro so it is the fastest
        Mini has a OCZ Agility 3 and it’s quick ( 3G )

        and my iMac has a owc mercury electra 3G 120 GB as the intel chip is 3G as well and the original Western Digital 1TB are the Fusion .. overall I’m happy I didn’t have to buy a new iMac and brought new life to 2009 late 27″ iMac

  • hi! I made a “fusion drive” from os x 10.8.0. After upgrading to 10.8.3, I got the newest Disk Utility, Version 13 (444). And on “about my mac” and I click “storage”, system display as Fusion Drive. Isn’t it the same? Or should I make the fusion drive over again from os x 10.8.3 installer? I just want to make sure I do have the true fusion drive.

    Thank you!

    • OS X 10.8.0 did not have the correct software components to create a Fusion Drive – however you could have created a Core Storage Volume and named it “Fusion Drive”. Apple didn’t add Fusion Drive options until 10.8.2 – and then the correct build was found only on models that offered a factory Fusion Drive option.

  • Hi guys,

    Upon entering Startup Manager (Option), there are two Hard Drives which are both my Fusion Drive. I thought its supposed to be a single volume?
    And where does the Recovery Partition gone to?


    • Apple seems to have removed the recovery partition from the Startup Manager. The best way of entering the recovery partition would be holding down “command” “r” during the startup process.

      The Fusion drive should be showing up as a single drive in the Startup Manager. It would be best to verify in Disk Utility only 1 partition is created. Also within System Preferences’s startup disk preference pane check to see if only 1 or 2 options are showing for the Fusion drive. If multiple partitions are showing up and you did not intend to do that, I’d recommend to erase the Fusion drive and recreate it.

  • In your example you show an SSD at “disk0” and an HDD at “disk1” and you issued that part of the “create” command as “disk0 disk1”.

    I had an iMac 11,1 and added a Mercury EXtreme Pro 6G and it, the SSD, came up as “disk1” but I was on autopilot and issued the same diskIDs in the “create” command, “disk0 disk1” … is this OK? It _seems_ to work right. I would think that ‘diskutil’ could figure out which is which.

    Am I OK or do I need to start over from scratch?

    • Your new Fusion drive should be setup properly if you followed through In Step 10 – Find Your Disk IDs: (individual results may vary) and Step 11 – Create the Fusion drive array.

      If you are unsure I would recommend running tests on the new drive to see if it is behaving like a Fusion drive should.

      • Thanks for the reply,BUT, neither the article nor the reply answers my question …

        When issuing the command ”diskutil cs create drivename driveIDs” is the order of the diskIDs important????

        Let us say, that the SSD is “disk1” and the HDD is “disk0” … In this case is it required that you replace “diskIDs” with “disk1 disk0” (in order SSD then HDD) OR does the order of the diskIDs NOT MATTER ???

        • Brian, from the testing I did it looks like the first ID passed to the ‘diskutil cs create’ command is presumed to be the ‘fast’ drive. I can’t say this with certainty but on the three pre-10.8.3 systems I tried, they all took the first ID and persisted to that preferentially irrespective of the specs or type of drive. I hope that helps.

  • Hi,

    thanks for your efforts.
    I’m also thinking about creating a fuion drive and started researching.

    I’ve an 21″ late 2009 iMac.

    I found an article saying that a fuson drive can be created but the OS can not boot off the SSD. It will sit on the HDD due to the used EFI and it will not be able to boot if it’s on the SSD part of the fusion drive.

    Can you confirm this? I’m a bit unsure as I truly wan’t to have the OS completely on the SSD part of fusion.
    This article can be found in a german Mac magazine with high reputation (Mac&i, iss. 9 pg. 152).

    Thanks in advance,

    • Great question and sorry for the delayed response. Our testing has shown that once the Fusion drive is created data is written to the SSD first and than overflows to the HDD. Since the OS is normally the first thing written to the drive it should reside on the SSD.

      Through our testing we have not seen any proof of smart data migration. That meaning that commonly used files that are stored on the HDD are moved to the SSD and rarely used files on the SSD are moved to the HDD.

  • Your videos do not cover how to install the second drive in a late 2012 iMac 27″. Is that not possible?

    • We currently do not carry a compatible SSD, so there is no video to make at this time.

    • Aren’t the fusion drives in these (CTO) iMacs already physically 2 separate dives- a 128GB SSD and a 1TB or 3TB ?.
      So shouldn’t it be possible to either “un-fusion” them or to put in your own replacement SSD ?.

      • I’m thinking of a set-up for video editing where I’d keep applications permanently on the SSD and be able to control capture of media files to the regular HDD. I’ll probably end up going with external drives if this isn’t doable.

        • The issue remains that we do not have a compatible SSD at this time to replace the Apple SSD in the 2012 iMac models. Down the road, once a compatible SSD is released, then that shouldn’t be an issue.

  • aaah please help!
    i did all and step by step with teh right ML version. i create a logical volume, but the next step to createVolume … jhfs+…
    comes an error: -69780: unable to create a new CoreStorage Logical Volume

    and now?
    please help,
    greetings tom

    • This is an odd issue. 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.

      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 through Speedtools or Drive Genius

    • I’m getting the same error.
      I Erased both the drives, Verfied the Disks after a clean disks, I reran the Process and it gave me the same error. Frustrated :(

  • Wonderful article, and I would like to try. My drive as three parts, disk0s1, disk0s2 etc. Each refers to a different partition. Can I use a partition instead of a drive identifier?

    • Creating a fusion drive will only work with the physical disks, there is no way of using a single partition. When you create a fusion drive it will delete any existing partitions on the drive.

      You may create 1 additional partition once the fusion drive has been created. This partition would only exist on the hard drive and not benefit from the fusion drive.

  • 2 questions:

    1.) Does Fusion Drive use a larger cache area than 4 GB by default, when you use a larger SSD than the stock 128 GB Apple SSD?

    2.) Can you somehow tinker with the size of the cache area during FD creation or later via plist / driver mods?

    Using a larger cache area than 4 GB would mostly eliminate any performance drawbacks for Pro Photo/Video users you mention in your article, while keeping the convenience of a single boot drive.

    • Unfortunately the 4GB cache space cannot be modified. No matter the size of the SSD that is used the space will remain 4GB. We certainly agree that being able to modify the 4GB free space would be a very beneficial thing.

  • You guys need to write a small GUI for the fusion drive setup…

  • What is the build number of the 10.8.3 version of Disk Utility which is the correct version to make a Fusion Drive
    function correctly?

  • Hi,
    does it really works with a MBP 15” early 2011???

    Thanks for help.

  • Hi, thanks for taking the time to clear up so many uncertainties. Much appreciated.
    one outstanding question i have is regarding TRIM. does it even apply in a fusion drive setup? is it necessary to use some dodgy 3rd party app to turn it on? does it depend on if you use an OWC ssd or another brand of ssd in the fusion drive?


  • Two questions;

    1. Can I use an already partitioned hdd with both a bootcamp partition and a mac partition, using the mac partition as part of the fusion drive?

    2. if the sdd drive I decide to use (250 gig) is smaller than what my files are (320 gig) will I still be able use the fusion drive, which would have a total of 900 gig? (900 gig = 250 gig sdd + 650 gig hdd partition)

    • When creating a Fusion drive, all the data that existed on the SSD and Hard disk drive are going to be destroyed when the 1 larger Fusion volume is created. So unfortunately the bootcamp partition you currently have will not be saved as a separate partition when the fusion drive is created . Here’s additional article about creating a bootcamp partition(s) on a fusion drive after it has been created: Create partition on Fusion Drive

      When you create your fusion drive your 250GB SSD and 650GB hard drive would be seen as 1 bigger 960GB volume. After the Volume has been created (Step 13) you then will migrate (Step 15) the 320GB of footage you have onto your new Fusion drive.

  • Hi all, good to hear that Fusion is now possible on older macs.

    Couple of open questions though:

    1. I did a fusion setup on my Mac Mini 2011 with 10.8.2. As Michael says it is not a real fusion drive as the storage tiering doesn’t work. Also as a side effect the repair partition on HD was not accessible any more and on boot selection screen two Mac Hds are shown (many people confirmed these problems.)

    So question is: If I do a fusion from scratch from 10.8.3 bootable usb stick will these two probems still be there? Or have they been resolved?
    2. If I restore my existing 10.8.3 data from a time machine backup or clone after redoing the fusion drive will it work? Or is the reinstallation of OS mandatory to activate storage tiering? So no data migration but playing back a complete clone.

    3. As the process of creating the fusion drive is the same than before but this time you claim with 10.8.3 storage tiering is activated, could you maybe give a little more insight on how you determined that and how it can be tested?


    • The recovery partition is not an option on a RAID volume, which is essentially what a Fusion Drive is. So, that isn’t something that is a problem, per se.

      You will want to follow the instructions and reinstall 10.8.3 from scratch. The key here is that the installer as downloaded from the App Store contains the required software components. The Software Update method does not.

  • OK. I followed your DIY instructions a while ago. Great! Is there any need for understanding how to UNfusion a drive? If I exchange one drive for another in the future – and want to reuse that drive as another separate drive – the ID of that drive is connected to the original fusion – if I get it right? Or have I misunderstood something? Please correct me/inform me…

    • 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”

  • I have a 2012 Mac Mini and I understand I can use the older described method. I purchased this Mac Mini with the intention of creating a Fusion drive before I put it into actual use, so I have nothing on it that needs saved. Can I use this new thumbdrive method and skip the importing/ migrating section?

  • Hi –

    I am trying to follow these instructions. I was able to download a copy of Mountain Lion from the App store, and moved it from the Applications folder to the desktop (had to drag it; it kept making an alias). Then I inspected the package and drilled down to the InstallESD.dmg file, and pulled that over to the desktop. This did not require an drag but the Finder did ask for my password.

    I opened disk utility and… it does not show up as a disk. I see my 251 GB Apple SSD, a 750 GB WDC (the two drives that came built-in with my MacMini Mid-2011, and my 2 TB Seagate (which appears also as my Time Machine drive).

    I was initially also seeing a flash installer and uninstaller — I cleaned those out of my Download file and they disappeared from Disk Utility.

    I rebooted — still no InstallESD.dmg showing in Disk Utility yet… there it sits on my desktop.

    Any ideas?


    • Double-click the disk image to mount it on your desktop. It should then show in Disk Utility.

      • Thanks Michael –

        I also discovered that clicking the restore tab and then clicking the “image” button gives me a browser window with .dmg files highlighted. When I selected the InstallESD.dmg it appeared in the left panel.

        Next question (sorry if I should know this) – I connected an old laptop drive using the NewerTech universal adapter to use as the target for the InstallESD.dmg. Under the Destination field in the Restore tab, it says:

        “Erase Destination and copy the contents of “InstallESD.dmg” to it.”

        She Who Must Be Obeyed has told me we must Must MUST have a copy of the old laptop drive (?).

        Can Disk Utility (or some other, simpler function) be used to copy this old drive without erasing the target? It’s just a 160 GB; my back up drive is a 1TB, so there’s plenty of room on it.

        Thanks again!

        • If the 160GB drive only is a storage drive and does not have an OS that needs to be preserved I would recommend to click and drag the files onto a folder on your backup drive.

          If the 160GB drive has an OS you need to preserve. You can create a disk image file (.dmg) of your 160GB disk through Disk Utility. This disk image file can than be restored back to the 160GB drive once you are done creating the fusion drive. To create a disk image file within Disk Utility, select the 160GB drive’s partition (the indented drive icon) and go to the File Menu then “New” then select “Disk Image from ‘volume name.'” You can save this image directly to your backup drive.

    • Success!

      I did have a little trouble (as noted below) but eventually got everything figured out. Ironically (perhaps) the Terminal stuff was the easy part.

      I was a little put-off to see that after the restoration I know longer have the old Apple version of Java — had to download Version 7 from Oracle. Shouldn’t be an issue for most but I have an app I use that wants the old version of Java.

      Frowny Face.

      For the curious, I’m using a Mid 2011 Mac mini with Apple supplied SSD and internal HD. When my daughter returns from college we will repeat this process on her 2008 laptop.

  • I’m getting confused :) I upgraded my system to 10.8.3, and then followed the ‘Internet described method’ making a core storage volume. Now I wonder if I’ve got a fusion drive or not… How may I find out?

    • So, there is no known way, like a terminal command, which may help establish if we actually created a Fusion drive?

      • Diglloyd actually has a great breakdown that shows how to verify your drive is fusion inside disk utility through a “first aid” check. Check the section titled “Viewing the ready-to-use volume“.

        • Thanks, Eddie! I had a look at it, but frankly I failed to see the difference between when there is a Fusion drive and when just a JBOD in a core storage volume… Got my limitations, sorry… My drive reads similarly to his in Disk Utility, but then again it seems to me he concludes at the end og the article that his set up is not a fusion drive after all? He used 10.8.2, so that corresponds with this article. So, still confused! :)

          • What I would recommend would be to Run the diglloyd Disk Test outlined on http://macperformanceguide.com/fusion-speed.html and wait until it has the speed drop associated with the SSD being full. Then, like Lloyd did in is test, let it sit for a while.

            If it’s a Fusion drive, theoretically, 4GB of space should be transferred from the SSD to the HDD during this idle time.

            So how do we test whether it has moved or not? Run the speed test again. If you’re getting SSD speeds that drop to HDD speeds after about 4GB of writing, then you probably have a Fusion drive. If the speeds start at HDD speeds and stay there, it’s probably NOT a Fusion drive and is simply a plain CoreStorage JBOD array.

            • Alternately, 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.

  • Hello I would like to add a second drive to my 2010 macmini 4.1 with a datadoubler but dont really see any listed for this model. would love to make a fusion drive. cheers

  • I have another question;
    After you have manually created your new Fusion drive ( the 1.1Tb in your example for instance ) and you then exit Disk Utility and continu as described regular the OSX 10.8.3 setup to Utilize this 1.1Tb drive; does then CORRECTLY a proper RECOVERY partion get created.

    i.e I strat of blank in my Mac that has 2 drives ( SSD and a HDD );
    Via the USB boot key ( the extracted install_esd.dmg ) you launch the installer
    By hand you create a new Volume ( the FUSION action )
    The installer continues; OSX gets loaded;
    My system reboots ( the bootable USB key is gone -> I am running my Mac from the Fusion drive )
    Do / has 10.8.3 installer properly utilized this drive now so when I do an “option – boot” My recovery partion is there and fully functional?

    Have you tested this / can you comment on this?

    • Fusion drives can be thought of as a type of RAID – of which a recovery partition cannot be written to. So on computers with a Fusion Drive, Internet Recovery is your only option.

      • “Fusion drives can be thought of as a type of RAID – of which a recovery partition cannot be written to. So on computers with a Fusion Drive, Internet Recovery is your only option”

        I don’t think that’s right.

        When I experimented before (and I never got real fusion, just a working logical volume, part SSD and part HD (cold fusion?)), I did it by using “diskutil cs convert on my existing updated 10.8.3 boot disk (which worked fine, even though I was booted off it at the time), rebooting and then using addDisk and resizeVolume. Apart from lack of dynamic data migration, everything worked fine.

        under diskutil list the SD drive looks like
        0: GUID_partition_scheme *240.1 GB disk0
        1: EFI 209.7 MB disk0s1
        2: Apple_CoreStorage 239.2 GB disk0s2
        3: Apple_Boot Recovery HD 650.0 MB disk0s3

        and the recovery partition boots OK

  • I want a fusion drive in my mid-2011 21.5″ i7 iMac, but I just don’t have the time for the physical SSD installation and the software chicanery necessary. I notice that I can get the SSD installed with your turnkey service – is there an option to also have OWC handle the Fusion initialization and OS installation?

    I have my own backups and can handle a re-install from there, but would prefer not to do take an entire Saturday to do the hard part myself.

  • After creating the Fusion drive and installing OS X 10.8.3, can you then create a Boot Camp partition to run Windows using the standard method? Did you guys at OWC try it? Thanks.

    • We have not tried it, but Apple’s Support Page on the topic does indicate that Boot Camp 5 can be installed on computers with a Fusion Drive. “Use the Boot Camp Assistant to create a Windows partition and install Boot Camp. The Windows partition will exist on the hard disk drive, not the Flash drive, and is not part of Fusion Drive Logical Volume Group.”

  • Hi. Would really like to perform this upgrade as described, but have read conflicting statements about creating core storage with MacBookPro8,2. Will 10.8.3 play nice with Fusion drive on a MBP8,2? If so, what is the recommended hardware setup?

    • Brady, you have me at a loss. Not sure the “conflicting statements about creating core storage” you’re referring to.
      However, this article is the result of our testing on the machines specifically listed in the article (of which the MacBook Pro Early 2009 model would be included in the “MacBook Pro (Late 2008 or newer) with Data Doubler” listing.
      So, you would need a 2.5″ SATA Hard Drive, 2.5″ SATA SSD, and a Data Doubler to be installed in your MacBook Pro as well as a backup of your data and separate 8GB or greater drive for the OS installer. Then follow the instructions above.

      • Sorry – I have read posts on Macrumors that some users have been successful at creating a Fusion drive for Early 2011 MBPs, and others havent. Some people have flat out stated that creating a fusion drive on Early 2011 MBPs is just not possible. Some have argued that certain drives will work, and others say they have not had success with the same drive. With your experience, do you see it possible to create a Fusion drive on a MBP8,2, or would I just be wasting my money and time?

  • You say the Fusion drive is “not designed” to work with external drives. Does that mean it does not work? I’d like to make a fusion with my iMac’s internal 768KB SSD and an external USB 3 hard drive. USB 3 is as fast as internal for a hard drive, and since it is the slower of the pair anyway, I wouldn’t expect it to be hit that often.

    Will this configuration work?

    My new iMac arrived yesterday and I have a 3TB drive arriving (hopefully today). I intend to give it a try since I have no data on my mac to lose at this point :)

    • Close paraphrase, but the article states “Fusion is designed to work on internal drives only.” We wouldn’t suggest trying to set it up with an external drive as simply unmounting the external drive could break the Fusion setup – and with it, corrupt all your data.
      You would probably be better served by relocating your home folder to the external drive in this instance:

      • After fusing the drives they would be a single volume though. If you unmount the volume then both physical drives go offline. Short of yanking the cable out (which you shouldn’t do even for non-Fusion drives) it should be as reliable as any external volume.

        Putting my home on an external drive doesn’t solve the problem. Most of my high churn files that would benefit from Fusion are in my home directory so I lost all benefits by moving it to an external hard drive.

        Agreed, an internal drive would be better, but that is not an option since Apple doesn’t ship a 768GB SSD/3TB HD configuration option.

      • Certainly a non fusion CoreStorage multidisk logical volume works fine on a mix of external drives (but that is not the same as saying that it is a good idea). I see no reason to assume that fusion would be different.

        I’ve had it working with a SDHC partitioned in two. A Firewire drive partitioned in two. and a logical volume taking one partition from each. That gave me 3 working volumes. Pure SSD, Pure HD and fusion.

        If I removed either physical volume then the CS volume vanished but on reinserting the disk, it would reappear.

    • I did initial testing with my new iMac and a manual fusion drive between the internal 768GB SSD and an external USB 3 3TB Mercury Elite Pro.

      It looks like fusion does indeed work in this scenario. It took quite a while to create more than 768GB of content using mkfile and copying files around). But eventually I created enough content to spill over to the hard drive and verified through iostat that it was indeed migrating data after 2 reads from the hard drive back to the SSD.

      In this configuration it still seems to have the same reserve buffer space (8GB ?) even though the SSD is much larger.

      I seem to not have a recovery partition though, so maybe I need to reserve some space before creating the fusion drive.

      I did some robustness testing. If I powered down the external drive and then booted n verbose mode, the system hung waiting for the root volume to appear. Turning on the drive at this point continued the boot process as normal.

      While the system was running I turned off the external drive (don’t try this at home!). The system soon froze to a halt with errors in syslog about disk2 not being available. Interestingly enough it didn’t kernel panic. Turning the drive back on did not unhang the system. I had to reboot and it went through a normal journal rebuilt process as with any other hard crash and then booted up as normal.

      So the end result is that it is possible to configure a 3.75TB Fusion drive in this configuration. I don’t plan on running in this way, but I wanted to know if it was technically feasible for some time in the future where the internal 768GB starts getting cramped. I wanted to know what my expansion options are.

  • What was the caveat you had regarding the release of 10.8.3 with regards to Fusion drive?

    • 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.

  • Hi

    I have mini (late 2012) with 10.8.2 (as you said it before – this model is FusionDrive capable from the beginning) upgraded to 10.8.3.

    Do I really need to boot from USB drive with full 10.8.3 on in this case?
    Is there a possibility that I have a wrong version of Disk Utility on my recovery partition?

  • Hi!

    using a mid 2010 15″ MBP. will this method work?

    I will be installing a 256GB SSD in the HD bay and 1TB in my optical drive slot.

    on 10.8.3 already.

  • I have a few questions:

    Is it possible to use a SSD larger then 128GB (say a 256GB SSD)? Would there be a benifit to that other than storing more files on the SSD portion?

    Also, say I decide to purchase a 256GB SSD can I create a partition and use one half for the fusion drive and the other half as a scratch drive for importing video files? I usually backup my video files on an external drive anyway.

    Your comments would be greatly appreciated.


    • You can use a larger or smaller capacity SSD – the larger the SSD, the more storage can be on the SSD itself.

      The instructions we give are going to use the entire capacity of the SSD in the Fusion Drive.

  • Howdy!

    Like the guy above, I also made a Fusion Drive with 10.8.2 as a test, using the instructions on the internet. I have a 2009 MBP and used a OWC 256 SSD for the SSD, and a 1 Tb rotating drive in the optical bay.

    Overall, I love it. Performance had been great, and I have about 370 Gb of stuff on it, so I know that the Fusion effect is working. Startup and app loading is at SSD speed.

    One question though, when I was setting it up, I misunderstood the sizing of the Fusion drive, and made the Fusion size 1 Tb instead of 1.25. The drive seems to be working fine. Are there any side effects other than I am not able to access the missing .25 Tb?

    • We did setup a few Fusion drives and shorted the space on them like you did just to test out if there would be any issues once the space was full.

      While we didn’t do any real extended testing this way, our short term drive fill tests found no issues aside from losing the neglected storage space itself. It acted just as if you had a 750GB HDD instead of a 1.0TB HDD installed.

    • try

      diskutil cs resizeVolume 111111111-2222-3333-4444-5555555555555 1262g

  • I think you also forgot to mention the write buffer, which is a big part of why Fusion speeds up your Mac.

    I followed the jollyjinx tutorial on my MacBook running 10.8.2. I have a 120 GB SSD, with 240 GB of data total on the Fusion drive, so I can assure you the SSD is full. Using the exact testing that jollyjinx does (using iostat), I can confirm the following happens when I create new files:

    1. They are written to the write buffer of the SSD
    2. Once the write buffer is full, they are written to the HDD
    3. Once I stop writing new files, all the files are moved over to the HDD
    4. I repeatedly read the new files, and they are moved over to the SSD in the background

    To me, this exactly described what Fusion drive is supposed to do: have a write buffer on the SSD, and move over often-read files to the SSD.

    So I’m a bit baffled on how you can assert that the jollyjinx method doesn’t work? Perhaps its a difference between newer Macs and older Macs? Maybe Macs that installed 10.8.2 from scratch have the required version?

    • From what you’re describing, your method does seem to be running a true Fusion setup.
      However, in all our testing (and by enlisting the help of some outside labs as well) we were unable to replicate your results while adhering to our strict criteria for updating the software components.
      We did test using a MacBook running 10.8.1 and simply could not obtain the updated version of Disk Utility required via either Software Update or direct download of 10.8.2 from the Mac App Store.
      Now that 10.8.3 is available, we were able to use that same machine to download the full version of 10.8.3 (the Software Update method did not yield the same results) which has the correct build of Disk Utility in the Recovery Partition necessary for setting up a Fusion Drive.

      • Interesting. I’m fairly sure I was on 10.8.2, and I wish I’d kept better records, but I *think* I formatted using the recovery partition. Maybe that was the trick? Either way, I was waiting for your final word on this before I started recommending my setup (Data Doubler + SSD + Fusion) to all my co-workers.

        I guess the point is moot now that 10.8.3 is out – but for those who followed the tutorials and don’t want to redo their setup, I think the best way to test if you have true Fusion Drive is to see if they have the 5 GB write buffer. The jolly jinx tests would work.

  • I need a SSD drive in my 2012 imac. Should I opt for the 768GB flash drive option that comes with the 2012 imac, installed by Apple, or can you guys install a SSD drive?

  • Assuming I already set up a DIY “Fusion Drive” in 10.8.2 using one of those earlier reports found on the internet, does that mean the automated storage tiering is now enabled for my DIY Fusion Drive after upgrading to 10.8.3, making it work as intended?

    • No, thus the reason I wanted to explain the difference between the Core Storage Volume setups that we were seeing across the web, and what is needed to differentiate them from a true Fusion drive. It takes more than naming your Core Storage volume “Fusion” to get that automated tiering to work – for that, you do need the correct version of Disk Utility.

      • The guide I used to set up a DIY Fusion Drive in 10.8.2 uses 100% identical commands to what has been posted here. That’s why I’m confused. I don’t see anything in the instructions posted here that differentiates from what I have done under 10.8.2, other than the fact that I was using 10.8.2.

        • The difference is the version of Disk Utility used to create the Fusion drive.

          • Very interesting about the need for Disk Utility from 10.8.3.

            Would this also explain the many articles on the Internet saying that the OS X wasn’t really migrating most often used data to the SSD?

            • It would indeed. The major component that is necessary is the correct version of Disk Utility in the recovery partition. With 10.8.2, that correct build was available with machines that had a Fusion Drive as an option only. So, those that used that version of 10.8.2 were able to setup working Fusion Drive while the rest setup a Core Storage volume only. Now that 10.8.3 is widely available, the correct version can be obtained via download of 10.8.3 from the Mac App Store.

    • Read the blog post on the jolly jinx blog and do the test yourself. If Fusion is working for you (it works as advertised for me on my MacBook running 10.8.2), don’t go through all the trouble of reinstalling.