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Rocket Yard Guide: How to Create Your Own Fusion Drive

One of the newest technologies available with the latest Macs is the ability to have what Apple calls a Fusion Drive. This is essentially a Solid State drive and a platter-based drive combined into a single volume. Apple’s underlying Core Storage technology then uses the SSD for the OS and frequently-accessed files, which will benefit from the speed, while placing lesser-used files on the larger, but slower platter-based drive.

The practical upshot of all this is that Fusion gives you roughly the performance of an SSD, while also taking advantage of the plentiful storage of platter-based drives. However, you don’t need to have a Fusion Drive from Apple to do this; with the proper command-line version of Disk Utility, you can create your own array with any platter-based drive and any SSD.

Of course, there are a few caveats to this setup (or the stock Fusion Drive, for that matter) that you should consider before committing to a Fusion setup. We’ll discuss those in a bit. First, though, let’s look at the process of actually setting it up.

Setting up a Fusion Drive

Items Needed:

  • A 2012 Mac mini – this is an absolute requirement as these are the only machines that currently have a version of Disk Utility that can create a Fusion volume.
  • 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 – 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.

Step 1 – Make sure you’re up-to-date.

Make sure the OS on the mini’s drive is updated to 10.8.2 or later. This is absolutely necessary, as the proper version of Disk Utility for doing this is on 10.8.2 or later on the mini and you want the OS versions to match.

Step 2 – 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 3 – 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 mini.

Step 4 – Boot to the external drive.

We need to boot to the version of 10.8.2 that came with the Mac mini, but since you can’t erase the drive if you’re booted to it, simply boot to your clone by holding down the Option key at startup and selecting the external drive you cloned to (it’ll have the orange icon). Then, log in to the desktop like you normally would.

Step 5 – 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 6 – 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 7 – 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 8 – 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 9 – 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 10 – Boot to your clone’s Recovery Partition.

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

Boot to your clone’s Recovery Partition by holding down Command-R at start-up.

Step 11 – Install OS X

Once booted to the Recovery Partition, select the option to Reinstall 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 12 – 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. Select your clone and Migration Assistant will bring over your data.

Step 13 – 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.

OWC Chris S.
the authorOWC Chris S.
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  • I bought my 27″ iMac last June, so I think I’m good to go with this setup.

    Would you mind providing links to what what SSDs and other hardware/kits we would need to purchase to pull this off?

    Also, how would you rate the dificulty of the hardware installation and software configuration on a scale of 1-10?

    This is great that you guys do all this testing and find these things out. This will be a great way to really speed up an older iMac. :-)

  • Trying to work out by these posts if I can set up a fusion drive on my late 2009 iMac. I have a data doubler installed with a 120GB SSD and the factory installed Hitachi 2TB 3.5″ SATA HDD. I have a copy of the latest mountain lion installed on a flash drive 10.8.3. Can I create a correctly working fusion drive setup?

  • hello OWC, im not a tech geek but i bought late 2012 imac a month ago 21.5 base model no fusion. So you guys are saying i can create a fusion drive using a external SSD and disk utility? i really want a faster imac 5400 rpm is not cool, please help.

    • No, both drive need to be installed internally – as we do not have an SSD upgrade for the 2012 iMac – the factory option was the only Fusion option available for that machine.

  • I am wanting to buy the base model $599, late 2012 Mac Mini and create a fusion drive…is this possible (space inside and the correct firmware)?

  • Hi,

    I can confirm that previously “selfmade” fusion drive still works after 10.8.3 combo update. Had to reenable trim. Disk utility showed no errors when checking the drive.

    To OWC: I recently did the fusion of 256GB SSD and Hitachi HDD in my Mac Mini mid 2011 via terminal from USB 10.8.2 ML. With the usual effect that Recovery partition is not accesible anymore and bootscreen shows 2 MAC HDs to boot from.

    Question: Will anything change in that resepct if I redo the whole process with 10.8.3? Will fusion be fully working and recovery partition be there again?

    • I’ve gone through many of these points already in comments on this article, but figure a re-hash is appropriate…

      There’s been a lot of confusion about what exactly a Fusion drive is. 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 makes the Fusion drive 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. So far 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 to the HDD. The way a Core Storage volume works, really makes people think they’ve created a true Fusion drive.

      That said, unless you’ve hacked your recovery partition of 10.8.2 on your 2011 Mac mini to be running the version released with a fusion drive equipped 2012 Mac mini or iMac, you are most likely running a Core Storage volume.

      We are currently testing out the recent update to OS X (which 10.8.3 shouldn’t break any existing actual Fusion drives, or manual Core Storage volumes created) and I will be covering all of our findings in a separate post once our testing has been completed.

  • Can anyone confirm that they they are able to setup the Fusion Drive with automated storage tiering on something other than the 2012 Mac Minis / iMacs?

    I have a 2011 iMac, and I would love to get a small SSD and set this up to increase performance, but there is a lot of conflicting information in the comments.


  • Will this work on the i5 entry-level 2012 mini as well? There’s no fusion option for this model but the hardware is identical. Thx.

    • If you purchase base model 2012 Mac Mini and install an SSD or 2ndary HDD it will prompt to create a fusion drive in the recovery partition.

      I purchased a brand new 2012 base model 500GB mac Mini, took out the HDD, put in 1TB+120GB SSD, booted from factory 500GB recovery partition, launched disk utility and prompted to create a fusion drive and im set. No command line info, or anything its automatic.
      system is fast, smooth and process was seamless.

      Would love for this to work on my 2011 iMac with 256+2TB combo…..something about this Core Storage set-up doesnt seem straight and dont think it takes advantage of the Tier storage mix….maybe i’m wrong??

      • Correct. Core Storage is only one part of the Fusion Drive and while Core Storage has been available in OS X since Lion, the automated tiered storage component which completes the true fusion wasn’t introduced until 10.8.2 and even then required a machine-specific build of the OS.

  • So this hasn’t been updated for a bit… are your comments still true since the release of 10.8.2 for all other hw platforms?

    Thanks and I really appreciate the info!

  • have a 2012 mac mini

    if I go thru the trouble of putting in 2 drives (concerned because of reports of broken-off parts of circuit boards
    with some people going thru the installation) – how much of an improvement in speed, and perhaps longevity,
    would I gain by upgrading the 1TB 5400-MB Apple Drive (Hitachi/Toshiba) for a 7200-MB drive- in a DIY Fusion.

    I do a bit of music recording, and usually a 7200 MB drive is indicated, at least for a second ‘write’ drive.

    I have 2 256MB SSD’s sitting around…

    if I install them in the mac mini 2012 – would they be ‘fused’ in some sense to be seen as one large drive?
    And how would this compare in speed and elegance to creating a raid0 volume?


    • A fusion drive runs at speeds that are almost identical to a single SSD.

      With the nature of how a Fusion Drive works, I don’t think you’d experience much of a performance change between having a 5400RPM versus a 7200RPM as the secondary drive in your Fusion Drive. Most of your real-time read/writes are happening on the SSD, while it is more of a background process in moving data between the drives.

      Two SSDs installed shouldn’t trigger any automatic Fusion rebuilding (although we really haven’t tested that)- the only “benefit” of doing so would be to create one volume out of the two drives – it wouldn’t make the throughput any faster. If you’re going for pure speed (and you like living on the edge) then a RAID 0 would be the fastest way to go. But – make absolutely sure you keep a bootable backup of your system. You’re doubling your chance of data loss from drive failure by booting to a RAID volume.

  • Total bummer. I was really hoping to configure a Fusion drive in my Early 2011 13-inch Macbook Pro.

    Thanks OWC for saving me the wasted time and effort. Especially since following these instructions would likely result in it appearing that I have a Fusion drive. Only to later realize a performance decrease after my 120gb SSD fills up and my Macbook starts only using my slow spinning hard drive.


    • I’d recommend you read through the whole list of comments before you decide. There are quite some who tell a different story. ;-)

  • Hi,

    I just bought a Mac mini late 2012. Installed an SSD in there and made the manual Fusion Drive configuration.
    Since there my mac is very slow and I can’t understand. Well sometimes it is indeed speed, but most of the time it freezes for 10-20 seconds every minute or more.
    My Mac mini is almost unusable..

    I tried to format and reinstall the whole thing, but still not solved the problem… any idea?
    Thank you very much… I’m lost!

  • I have a 27″ iMac and a late 2011 MBPro 15″ running 10.8.2. Any thoughts at this juncture whether the Disk Utility provided with the 27″ when transfered to the MBPro will create the new fusion drive. An OWC 6G 240gb SSD and 5400 rpm Toshiba 1.5tB HD is envisioned as the target. Thank you.

    I should clarify that the 27″ iMac is equipped with a factory 3tb fusion drive. The OWC SSD + HD would be installed in the 15″ MBPro.

  • Any clues on what would happen if you physically moved an existing Fusion Drive pair (built in a 2012 Mac mini) into a 2012 MacBook Pro with a Data Doubler?

    • As part of the Core Storage setup for the Fusion Drive, the SSD and HDD are referred to by how they appear to the system (drive0 and drive1). *IF* you mange to install them so they appear the same way in the MBP as they do in the mini, *MAYBE* it’ll work. That said, though, it is something a.) we’ve not tried in-house so it is something b.) we cannot recommend or endorse.

  • I have a new late 2012 2.6Ghz Mac mini and the requisite components for a DIY fusion except for a spare hard drive to clone to. I don’t have any data on the stock 1tb drive that I need to keep. How do I get the fusion drive setup software wise? Can I just rely on the Internet recovery process? Do I still need to somehow get into Termial and go through the above Disk Utility process? Thanks.

  • I have a MBP early 2011. I recently installed a ssd Hyper x 120gb in the main place where hdd is usually and the hdd to the optical bay. My problem is that I can’t do the Fusion drive, it tells me that was an error and restores my ssd from 0 and then tells that it can’t recognize the ssd.


    • This is one of the reasons we don’t recommend this for any models other than those that have a factory Fusion Drive option (the 2012 mini and iMacs) – results are inconsistent at best.

      If you continue to have troubles, you may want to try contacting the SSD manufacturer (Kingston, in this case), as we can’t offer any support for those drives.

    • The reason you cannot get fusion to work is because Fusion drive requires at 128GB on the SSD to work. anything lower will not have the required space to operate core storage.

    • The speed difference between the single SSD on its own and the same SSD in a Fusion drive setup is negligible for real world use.

  • FYI, this isn’t working on my new 2012 Mini 2.3Ghz ivybridge. “Error: -69888: Couldn’t unmount disk”. Any advice.

    Both disk show as
    disk0 – vertex 4 128GB SSD
    disk1 – apple 1TB Hdd

    Any help much appreciated.


    • Hi,

      I have a similar problem here when i tried to create the Fusion using “diskutil cs creat Fusion disk0 disk1”. disk0 is my SSD and disk1 is the original HDD that came from Apple. when Unmounting disk1, i got the error: -69888: Couldn’t unmount disk.

      Now i can’t boot back to my SSD and can only start my mac mini from the cloned recoveryHD partition.

      • I realised that the reason I wasn’t able to unmount the disk was because it was still in use. I had previously set-up my mac such that the SSD was the primary boot/app drive while documents were saved to the HDD. So after I had cloned the SSD boot disk to my external HDD and booted from the external HDD, the documents path was still pointing to the internal HDD. As such I was unable to unmount the drive. correcting the document path to point back to the external HDD solved the issue and I was able to proceed according to the rest of the guide.

        You probably will need to check if somehow, there is an application or document that is still using one of the drives that prevents the drive from being unmounted.

        Hope the above helps.

        • “correcting the document path to point back to the external HDD solved the issue and I was able to proceed according to the rest of the guide.” Can you provide instructions on how to do this?

    • You can force unmount a drive by running the following Terminal command:

      diskutil unmountDisk force PATH

      Replace PATH with the name of a volume on the disk you are trying to unmount.
      In your case the path should be /dev/disk0.

      It also happens to me, and this trick solved my problem.

  • Followed this guide and installed a 256GB SSD. 2012 i7 mini boots from off to login in 11 seconds!

    I Restored from a cloned recovery partition on an external drive and I now have a fusion drive with a recover partition.

  • I am still confused over one thing. My plan is to add a SSD to my new Mac Mini 2012 with the second HD kit I just received from OWC. I am almost finished with my initial Time Machine backup but I don’t know if, after I set up the Fusion drive system, my Time Machine backup will restore the recovery partition. I know you can use internet recovery to reinstall the OS but I am currently in Mainland China, and they are throttling downloads from Apple (god know why). What are my options to have a proper installation of the OS on the newly crated Fusion Drive that includes the recovery partition without me having to download a new version?

    • You have a couple of options. Since it sounds like you want to avoid downloading a copy of the OS, I would suggest the following approach. I think this will work, but since I don’t have a MacMini of the type suggested, I can’t actually try it.

      1) Download apple’s OS X Recovery Disk Assistant. (http://support.apple.com/kb/DL1433) This should allow you to place a recovery partition on an external USB stick which you can they use to boot your machine.
      2) Run the Recovery Disk Assistant and use it to create an externally bootable recovery disk.
      3) Update your TimeMachine.
      4) Boot from the stick and create your FusionDrive. Use the TimeMachine restore function on the boot stick to restore your drive.
      5) If you wish, try using the OSX Recovery Disk Assistant to create a new recovery partition on you new FusionDrive.

      Most other options available require a copy of the OS Installation file to have been downloaded from the Apple store and would involve using it to create a bootable USB installation drive. You can find plenty of guide for this approach online.

  • Can I ask a daft question? if after adding a ssd to my iMac on the spare sata socket, then i do:
    diskutil list
    If disk0 is my normal drive as I expect it will be and disk1 is ssd, when I goto create can i do:-
    diskutil cs create fusion disk1 disk0
    Will this make the ssd the first choice?

  • Hi!

    I bought an owc ssd mercury pro 6g and I’m willing to buy a Mac mini 2012 server. I want to replace the one of two hard drives that are installed in the macmini with the ssd and follow your procedure to make the fusion drive with the 1 TB hard drive and the 256 ssd drive. Will this work? If yes which of the two hard drives that are installed in the Mac mini i have to take out to replace with the ssd so the fusion drive to work properly?

    • That will work. OS X Server is an add-on to OS X so it still has all the functionality of the non-server version.

      From what we’ve seen, the OS is usually installed on the drive closest to the access door – so it is that drive you’ll most likely want to remove and put in an external enclosure to boot from in Step 4. (Although we have seen that reversed – you can boot and check disk utility to be sure. When you choose the drive and check the Partition tab it will state whether or not it is the boot partition.)

      Although, it isn’t the most cost-effective way of getting that setup…

      Our Data Doubler DIY Kit contains all the parts and tools you need to install that SSD for $39.99 – and if you need the server software, it is a $19.99 download from Apple. When you consider that we carry 1.0TB HDDs starting from $89.00, you can save over $50 starting with a non-server Mac mini and adding the extra components rather than purchasing the server at a $200 more premium.

  • Hello,

    Do you know how fusion drive compete in spedd against a Thunderbolt SSD Drive for boot volume ?

    Thanks !

    • Given the same single SSD in each setup, the speeds should be almost identical as both the internal bus on the thunderbolt-equipped Mac models and the Thunderbolt bus itself provide plenty of bandwidth for the drive to achieve its maximum throughput potential.

  • If I was putting this into a brand new 2012 mac mini with no important data, do I still need to boot off of an external drive?

  • Got my Mac Mini 2nd drive kit with 64Gb 6G SSD today. I followed the installation instructions and the movie then created the fusion array by following this article. The whole procedure was fairly quick and quite easy even for a new Mac user like me (This is my first Mac!)

    I just have a couple of questions –

    1. How can I be certain that my fusion array works as it should? Using BlackMagic drive speed test I measured roughly 80Mb/s write speed and about 180Mb read speed. Is this normal? This is way below the rated speed for the SSD drive and resembles the HDD speed, which I clocked prior to starting the process at 80/80Mb.

    2. After reading many of the above comments and other sources around the web, I realised that the SSD size most people choose is 128Gb and not 64Gb, like I have. Frankly, I didn’t do much homework before I ordered.. Did I make a huge mistake? If so, I guess I’d better correct it before filling my Mac with data, don’t I?


    • 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.

      For longevity of use, it is always suggested to get the highest capacity and fastest drives you can afford in order to get the most use out of them before needing to upgrade to larger or faster storage. If 64GB of storage is adequate for your current needs, then no mistake was made – you just may find yourself wanting to upgrade again a little sooner.

      • I really appreciate your quick response Michael! Happy new year.

        Thanks you very much for the information.
        Knowing that about the size of the SSD drive now, I think I’ll swap the OWC 64GB with an 120GB Corsair GTX SSD off my desktop PC. I’m thinking it would be up to the job, won’t it?

  • Why do you think only 2012 Mac Mini’s come with the correct version of diskutil? I had no issues creating the Fusion drive on my 2007 iMac….

  • Just followed your instructions for updating my early 2011 macbook pro and everything seems to have worked fine. The only glitch I found was that I couldn’t install the OS using apple’s recovery drive, probably due to having a cr@ppy internet connection, as I’d paid for Mountain Lion and installed it previously.

    It did let me install from a Time Machine backup across my home network, I just hope that it’s put everything in the correct place so that the Fusion drive works correctly, I’m certainly seeing much faster boot times but I’m not sure if they fusion drive is copying back and forth to the ssd as it should do, is there any simple way to check for that.

    Thanks for the help,


  • From what I’m reading, there’s not much point in this for my Apple SSD + OWC HDD 2011 MBP, which is cool. But I can’t help wondering – could this single Fusion volume be encrypted?

    I have encrypted SSD and HDD but for this reason it is not supported to move my home directory to the HDD. It can be done with some additional software, but is not supported.

    At this stage I’m thinking of unencrypting for the simplicity of moving my home folder rather than *most* of my stuff ending up on the HDD but bits and pieces slowly building up on the SSD as various bits of software make assumptions on where to put files.

    But if a Fusion drive could be encrypted, it would be the best of both worlds and the way to go.

  • If OWC took a 2012 iMac 27″ with a factory installed Fusion drive with a 128 SSD and a 1TB hard drive and replaced it with a 512SSD and a 4TB had drive could you then create a Fusion drive ?

  • Just getting around to reading this post after thinking I might do this on a 2011 iMac with an OWC SSD and HD.

    One question for OWC: does a home-brew Fusion Drive have any implications for firmware updates on the OWC SSD portion? I’m assuming the OWC Linux installer would see the SSD as a separate drive and that the firmware wouldn’t affect the HFS+ file allocation tables or anything like that.

    • You are correct, while OS X sees both drives as one “Fusion Drive”, the firmware updater still would recognize each individual drive.

  • I had you guys install a 120 GB OWC SSD into my 2011 iMac, so the hardware inside is almost identical to what’s in a Fusion Drive anyway. Does this procedure work if I want to set up my 1 TB HDD + 120 GB SSD as a Fusion Drive in a 2011 27″ iMac?

    • The 2011 Mac mini machines are the only models that currently have a version of Disk Utility that can create a Fusion volume.

      • I actually am switching to a Mac Mini (2012) that I received yesterday. I wiped the iMac and was trying to set up a Fusion Drive to up its resale value. I connected it to the Mac Mini in Target Disk via Thunderbolt, was able to create the Fusion Array, but then received an error message at the last step of OS X installation. It told me to repair the disk, but then I got various error messages while trying to repair the disk using Disk Utility. Ended up “un-fusing” them and backing out of the whole process and reinstalling OS X just to the SSD. I’d still be interested to pursue if you think it would work.

  • I just created a fusion drive by ignoring the warnings and letting Disk Utility from the recovery partition of a cloned external drive (2012 mini) do the “repairs” on a 256SSD and original internal 1T drive (about 12 seconds). It showed up immediately as a single drive and I’m installing the OS as we speak.

    I may have to go to terminal but since I’m terminally lazy I’ll post if this works as a good fusion drive approach “for the rest of us.”

  • Do you have to use the physical disk, or can you use a partition? It would be nice if this could be done while still keeping the recovery partition on the original drive.

  • I followed the steps above, except that, instead of re-installing the OS, I cloned my HD back on the Fusion Drive. Everything works fine, but I’m wondering if it’s just the same as having installed the Os first ?

    Thanks OWC, for your wonderful job on the tutorial !

  • Excellent work guys. Thank you very much for making this tutorial. I recommend you to everyone with a Mac.

    Have a great Holiday!

  • Has OWC made a video for removing the stock HD and installing two new SSDs? I wonder if there are any particular problems with this – would you have to first leave the HD in while you put one SSD in to transfer the OS (being careful not to create a fusion drive), then open it up again to swap out the stock HD for the other new SSD? I am planning to buy two 256 GB SSDs for less than the price Apple charges for one, and I’ll get a free 1TB HD as a bonus which I can put in an external enclosure and use as a back-up volume. If you could let me know whether this will work I’m ready to pull the trigger…

  • I am curious how the Fusion setup affects the SSD performance over time. It seems to force two things that, as I understand, are not generally recommended for SSD performance and longevity: the SSD will be almost full (only 4 GB free), and every new file (including large downloads) will be written to it. I suppose this isn’t so bad if the 4 GB free space sector moves around to ensure even wear of NANDs. Presumably Apple’s setup takes care of that, though I wouldn’t bet my life on it. But what manages the location of the free sectors? OS X, drive controller, drive firmware, or a combination of those working together? So, even if factory-supplied Fusion Drive distributes the writing evenly, I can still see how a DIY setup might not. I think it would be very informative to test both Apple-supplied and DIY Fusion Drive for performance over a lot of writing cycles. (And maybe for the DIY setup, also compare an overprovisioned 120 GB drive and a non-overprovisioned 128 GB one?)

    • These are all valid points and I’ll forward them on to be looked into deeper. If there’s any significant findings, you can be sure we’ll pos them here.

      However, those same points/potential pitfalls support simply just going with an SSD/HDD setup individually, with a relocated Home folder – I’ve used this method for quite a while now, and I’ve never had a day’s worth of trouble with it.

      • I just installed a Fusion drive on my 2010 model MacPro (240GB OWC SSD + the 1TB HDD my MacPro came with). This MacPro originally came with Snow Leopard. The Fusion drive works perfectly, and has boosted the MacPro’s speed very satisfyingly. To do it, I just re-downloaded the latest Mountain Lion installer, and set-up an external HDD as a Mountain Lion Install ESD using the instructions here: http://www.macworld.com/article/1167857/how_to_make_a_bootable_mountain_lion_install_drive.html
        I made sure I’d just done a TimeMachine backup, then booted from the external HDD and followed OWC’s Terminal instructions for setting up Fusion drive, then restored my set-up from TimeMachine. All went completely smoothly, so the latest version of the Mountain Lion installer on the App store seems to me to have all the CoreStorage commands needed to support Fusion drive on any Mac capable of running mountain Lion.

        • There’s been a lot of confusion about what exactly a Fusion drive is. 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 makes the Fusion drive 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. So far we’ve only seen that software component in the 2012 Mac mini models that ship with their specific build of 10.8.2

          • ” It needs the software to run the automated storage tiering to make it a true Fusion Drive. So far we’ve only seen that software component in the 2012 Mac mini models that ship with their specific build of 10.8.2″

            So to be sure I understand: the steps you described above will create a true Fusion Drive but only, currently, on the 2012 Mac Mini?

  • It would be AWESOME if you could make the 4TB Mercury Elite Pro and the 750MB Mercury Elite Pro mini to work as bootable Mac Fusion Drives in the future…

    • While there have been examples of using an external drive as one of the drives in a Fusion array, the underlying technology behind Fusion needs to see which drive is an SSD and which is an HDD. These identifiers are determined via SATA, which would require a direct, internal connection.

        • If it’s going through a bridge (like it would be if it were going through TB), info about the drive is not always transmitted. At this time, the only reliable way would be internally mounted.

      • I have a ExpressCard/34 Wintec SSD 24GB I’ve been using as my primary drive in my MacBook Pro for several months now. It was a big pain to get working, but works pretty well now.

        It shows up as a SATA drive in System Information, so I’m guessing I could use Fusion Drive.

        But I’m confused – I see OWC Larry saying this doesn’t REALLY work.

        Chris, is your experience that data does seem to be migrating appropriately?

        Or are you guys in agreement about what happens when?

        • There’s quite conclusive evidence (Matthew Griffin links to some of it, above) that some people who have created core storage drives ARE getting the automated storage tiering not just on the Macs that come with Fusion Drive.

          I’ve been through the latest EULA, and I think it specifically allows use of any version of Mountain Lion, including the special version of Disk Utility and or of 10.8.2 that is required on any Mac that has a valid Mountain Lion license. Besides, Disk Utility isn’t used to create Fusion Drives. Apple does say that “Earlier versions of Disk Utility can’t be used with a Fusion Drive.” But that’s hardly the same thing! It’s unclear whether the command line is required to create a fusion drive, as is, I believe, 10.8.2. If folks who have tried posted more info on what mac, what version of 10.8.2 and of Disk Utility they used, whether they used the command line or Disk Utility to make the Fusion Drive, and whether they get automated storage tiering or not, we’d be able to figure out what the critical steps were to take and avoid.

          • Having seen the detailed tests with iostat done on a standard 10.8.2 DIY Fusion Drive (not the special disk utility from the FUD Mac mini) in this post http://jollyjinx.tumblr.com, for me it is hard to still believe OWC Michael’s point, that you will create only a dumb core storage volume without any FUD intelligence that way. The numbers given clearly tell a different story.

            While I understand, that OWC doesn’t want to sell their SSD kit with any guaranty to work as FUD in any old Mac mini, it probably would have been better to issue a warning ” we cannot guaranty that it works”, than to say ” our techs have found that … it does not work”.
            I’d suggest your techs reevaluate their statement, following the procedure outlined in the link above and backing up their finding with iostat numbers in case they still hold on to it.

          • Mathew, readings this article (http://macperformanceguide.com/blog/2012/20121103_2-DiskUtility-nasties.html) makes me believe, that the special Disk Utility (GUI Fusion Version) automatically creates a Fusion Drive from a SSD and a HD. In fact it seems impossible to create separate volumes with this version. This would make sense, as you cannot expect the average user to go through terminal commands to rebuild their Fusion Drive if necessary. Looks like this GUI Fusion Version was made a bit in a hurry and we likely will see future Disk Utility GUI versions, that allow us to choose, whether we want to create a fusion drive or separate volumes.

            My 5 cent:
            To create a Fusion Drive with Disk Utilily (GUI version) you need the special version that comes with the FUD Macs.
            Otherwise you have to use the diskutil (terminal command) from any 10.8.2 installation.

      • “…underlying technology behind Fusion needs to see which drive is an SSD and which is an HDD…”

        Really drive speed is what matters.

        I might set up a Fusion disk with a 15K rpm 300 GB drive and a 7200 rpm 3T drive. So why can’t is just time the drives?

        Maybe it can have bore than 2 tiers

      • How on earth do you know that. Unless you have access to internal Apple documents then I think you are just guessing.

        Given the structure and flexibility of CoreStorage, I would expect to be able to build far more complex structures than that.

  • I can confirm that it is NOT true that a Mac Mini is required. I type this from my 2010 27″ imac. I followed a procedure roughly similar to the one outlined in this post, and it worked just fine. I’ve been up and running with my home brew Fusion Drive for about a month now.

    • As stated into the response to Ron Miller, our techs have found that when using any version of Disk Utility other than the one that came with the 2012 Mac mini, it will appear as though you have a Fusion Drive, but it’s really just a standard Core Storage volume – without the file moving and

      If you have it working as an actual proper Fusion drive, then consider yourself lucky. We did not experience that with our attempts of using versions of Disk Utility other than that which came with the 2012 mini.

      • Are you sure it is not possible to create a true Fusion drive on older Mac’s?

        You mention that it only works with the DiskUtility that comes with the 2012 MacMini, but surely this is usable on other systems or am I missing something?

        I would have thought it entirely possible to re-create a recovery partition with said Fusion compatible Disk Utility on any Mac unless your suggesting Apple have done something sneaky with firmware in hardware models shipped from 2012 onwards (I hope not).

        • The build of 10.8.2 that is required for setting up your fusion drive has only been released with the purchase of a 2012 Mac mini (and now the 2012 iMac models). Running on other machines at this time would technically violate the EULA and thus we listed the machine requirement in our post.

  • I am always impressed with how clever you all are at OWC !

    If one of the drives in a Fusion array fails would it be possible to boot from an external drive and then recover the data from the drive that did not fail ?

    • The data on the drives is linked together in a Core Storage unit. As such, if one drive fails, simply hooking up another drive and trying to pull files won’t work. While it MAY be possible to recover some files through direct reading of the disk (like through a data recovery service), it’s probably going to cost more than the returns are worth. If you’re doing this (or, really even if you’re not), it’s best just to have a reliable backup strategy in place.

  • You mentioned in the factory Fusion setup that, “Once writing is complete, data will be moved from the SSD to the hard drive until there is 4GB free on the SSD again.” This to make sure that any new data written (under 4GB) will be written to the faster SSD… But does this same “behind the scenes magic” that the factory Fusion setup does with freeing up 4GB of space automatically also happen with the aftermarket array setup you detail setting up yourself above? Thanks!

  • Thanks for the write-up! I’m curious, however, about the statement that this will only work with the diskutil on the new Mac Minis. There are other write-ups floating around where people have created fusion drives on older macs.

    I’m curious because I would really like to install a fusion drive on my 2011 Mac Mini.

    • According to our techs, when using any version of Disk Utility other than the one that came with the 2012 Mac mini, it will appear as though you have a Fusion Drive, but it will not behave as such. You would be essentially creating a standard Core Storage volume rather than Fusion. Effectively, once the SSD fills, you’re running at HDD speed for good; there is no 4GB migration or smart movement of data. That migration, of course is what Fusion is all about.

      This all may change once 10.8.3 comes out. Until then, your best bet is a HDD/SSD combination with the relocated Home folder. It’ll allow you a little more flexibility in what files go where anyway (especially useful when working with larger files).

      • Thanks for the response. On at least one website, the author did some detailed analysis showing that data did in fact automatically migrate from the SSD to the HDD and vice-versa. Do you know exactly what didn’t seem to be working with the older mac fusion drive? Is it the 4GB write cache that does not work properly?

  • Thanks for the writeup. Lloyd Chambers claims though that he cannot replicate the “smart ” migration in his fusion setup-that it just behaves like a JBOD. There are however various reports that it is successful on other hardware and with using stock 10.8.2 commandline like you did here. So, if you completely fill up the SSD are you seeing smart migration back and forth from SSD to platter using owc SSD, and have you created fusion on older hardware yet and tested the same?

    • Our results were as described – the SSD fills, then information is moved to the HDD until 4GB is free on the SSD again. The “smartness” of this data transfer is something that will likely need to be determined over time. Unfortunately, it’s difficult to say exactly what files are where on the drive, so direct measurement of “smartness” of data doesn’t seem to be in the picture at this time. However, usage and performance over time should be indicators of the actual efficacy of this kind of drive.

      At this time, we are only focusing on the Mac mini, as that is the only model that Fusion is officially supported on.

    • As far as Time Machine (or a clone for that matter) is concerned, a Fusion Drive is just another Volume on your Mac, just as it would see a single drive. It will copy the files into its format and restore them to wherever you’re setting them up.

      • I did the steps above on my brand new Mac Mini that I had backed up to a Time Machine on an external drive. (I just got my SSD and kit from OWC via FedEx. Everything appears to have connected perfectly)

        I created the Fusion Drive, but when I go to restore from the Time Machine it says that it can’t erase the restore volume on the target and forces me to restart.

        I’m in the process of just doing a raw install of OSX over the Internet Recovery and then trying to migrate my data later, but it’s not as straightforward as just copying the old stuff in recovery, apparently.

        • Yeah… Time Machine is not the same as a clone or direct copy of the drive, which this process requires. However, you should be able to restore from Time Machine after the Internet Recovery installation.

          • I can confirm that there are no problems doing it this way, i.e. just reinstalling OSX from Internet Recovery or otherwise and then using Migration Assistant to move your stuff over. Dropbox had to resync; that’s it.

            Is there any way we can confirm that we are really “fusioning” or whatever? My system is fast as hell all of a sudden, but I don’t know if it’s optimizing, etc.

            I have the late 2012 Mac Mini, but my recovery stuff was 10.8.1, fwiw

            • Same here. 2011 Mini. Cloned my boot drive with Carbon Copy Cloner, used the OWC kit to put in my second SSD, booted from the external and used Disk Utility to enter the requisite commands. It went off without a hitch, and when I cloned my stuff back over from the external, everything worked.

              I think you guys are being a bit conservative. I’m definitely seeing things writing first to the SSD, and then to the HDD. And as I use it, things I access more frequently are indeed launching more quickly. I really doubt it’s just working on blind luck — from what I can tell looking at terminal output, it is indeed behaving like a real Fusion Drive. You’re the only ones insisting that this most recent version Disk Utility is itself essential. From my understanding, doesn’t Disk Utility just access lower-level commands anyway, which is what all this terminal stuff is about?

              Anyway, I can confirm with some confidence that my install worked as advertised. I’m very pleased with it so far.

              • See my comment from earlier in the thread for a breakdown of terms…

                The “terminal stuff” sets up the Core Storage Volume (which is NOT the same thing as a Fusion Drive). The build of 10.8.2 is required for the automated storage tiering (THAT’s what makes your CSV a true Fusion Drive). That OS build, to date, has only been released with the purchase of a 2012 Mac mini (and now the 2012 iMac models). Running on other machines at this time would technically violate the EULA and thus we listed the machine requirement in our post.

                • Alright, you win. I don’t have a Fusion Drive. But I do have a very fast SSD and HDD which function as one volume and are working together so that my most-used data seems to be working from the SSD. Call that whatever you want. And thanks for the install kit, worked great.

  • There are lots of reports of MacRumors and other apple focused web sites about people who have “rolled their own” fusion setup, using terminal vs disc utility for the initial setup. I agree that most of us should wait until at least 10.8.3 to see if the new disc utility will be included for all of our machines, as that would probably make it easier.

    Hopefully the pieces will fall into place soon to buy a 2 bay thunderbolt drive, with a SSD & HDD included, making upgrade for older macs a simple process of plugging in the drive, and installing the OS to an external fusion thunderbolt.

    • Whoops, didn’t realize you still needed terminal with this setup, I thought it was something new. (It’s what I get for not reading it fully before commenting.)

      Hopefully someone will make a setup utility to make the process easier soon.