I have a Mac Mini with two drives: a 256GB SSD and a 500GB HDD. From what I've read, the new Fusion Drive does all of it's magic in software, using the Core Storage APIs.

Can I get my setup to behave like a Fusion Drive? That is, I want the two drives to appear as a single logical volume, with the system automatically moving frequently accessed files to the SSD. I understand that we can easily stripe or extend or RAID drives, but the automatically managed tiered storage features of Fusion drive would be great to have without investing in new hardware.

  • 1
    A few months ago @JessBowers commented on SSD storage life. I'm confident that the Apple-supported implementation of Fusion Drive will be considerate to the SSDs installed by Apple in Fusion Drive-branded Macs. I guess it remains to be seen whether in other Macs the software and firmware will be equally considerate to SSDs chosen by end users. – Graham Perrin Nov 4 '12 at 12:48
  • From 2009, another performance-oriented use of SSDs by Apple: Mac OS X Server v10.6: Moving an HFS+ Journal to a different volume. Hint: the feature is not limited to Server versions of the OS. For more about Apple_Journal slices, see the moveJournal verb of diskutil. – Graham Perrin Nov 11 '12 at 20:07
  • I successfully managed to add a SSD disk to my 2010 Macbook Pro, to create a CoreStorage volume and reinstall OS X 10.8.2 on it. Everything is working fine and the speed increase is really nice. – Davide Gualano Nov 16 '12 at 10:48

Yes, you can create a fusion drive on older Macs, described in full length here:

  • You obviously need both an SSD and a HD. Let's assume they are known to the OS as disk1 and disk7. You can check disk id by diskutil list.
  • diskutil cs create bla disk1 disk7 to create it, where bla is the name you give to the fusion drive.
  • diskutil cs list and take note of the Logical Volume Group ID
  • diskutil cs createVolume <ID from above> jhfs+ blub 100%, where blub is the name you give to the volume.

Link to Apple instructions: Click Here

Note: These are instructions to fix a split fusion drive, but work also for making one.

  • 2
    Awesome investigation! It's worth pointing out that you've successfully experimented with the same technique on non-HFS+ file systems as well... – Dan J Oct 31 '12 at 16:38
  • @Jolly I saw this on your blog and it’s awesome how soon you worked it out! +1! – duci9y Nov 1 '12 at 9:45
  • Is there a reference document for the diskutil commands? – George Nov 1 '12 at 10:29
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    Use man diskutil at the command line. – jtbandes Nov 1 '12 at 20:06
  • anyone know how to preserve the Recovery partition when you use this technique? – Jess Bowers Nov 3 '12 at 1:44

Yes and no.

The Fusion Drive is taking advantage of Core Storage to act as one logical volume, which you see as a single volume but can actually be made up of multiple physical volumes (in this case, an SSD and an HDD).

You can create and manage Core Storage volumes with the diskutil command in Terminal. (Disk Utility does not yet have extensive Core Storage support via the GUI.) In particular, you can create your own logical volume groups and logical volumes, with diskutil coreStorage createLVG and diskutil coreStorage createVolume, among other commands (see the man page for details).

My guess, however, is that the Fusion Drive's special behavior, automatically moving your data between physical volumes, is encoded in a special logical volume family, and this is probably not something you could mimic easily. (I'd be happy if someone could prove me wrong!)

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    It's also worth noting that until people actually have these machines in their hot little hands we will not know what Apple has done, and how easy it might be to make other setups look similar. – Paul Wagland Oct 25 '12 at 18:38
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    Apple has posted an interesting article (KB HT5446) regarding Fusion Drive. Any "handling" of the Fusion Drive requires an updated "Disk Utility.app" – Francis Ouellet Oct 25 '12 at 18:43
  • Without said "updated Disk Utility.app", would one be powerless to diagnose disk problems in a DIY Fusion Drive using only the "stock" Disk Utility? – Gorb Nov 13 '12 at 19:59
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    @Damian Presumably the features such as Repair Permissions would still work. I would guess that Verify/Repair Disk might work as well but you should confirm with someone who has tried it. – jtbandes Nov 13 '12 at 23:53
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    So now that "people actually have these machines in their hot little hands", is it known whether creating a logical volume as described all over the web actually creates a "Fusion Drive" with all the automatic file movement goodness or not? – tml Dec 21 '12 at 15:15

I just finished creating a DIY Fusion Drive in my early 2009 MacBook Pro. It works great, and I figured out how to keep my recovery and Boot Camp partitions at the same time.

I started with backups: Both a Time Machine and a Carbon Copy Cloner backup of my Mountain Lion partition, and a WinClone backup of my Boot Camp partition. All backups were saved to an external hard drive that wasn't involved in the Fusion Drive upgrade.

For hardware, I bought a 128 GB Samsung 830 SSD and a hard drive caddy tray that let me replace my Apple Superdrive with a hard drive. (The instructions that came with the caddy are completely wrong, but the caddy is simple enough that I figured out how to install the drive in the caddy anyway.) The installation was tricky and required a tiny Torx screwdriver and some spudgers, but the instructions on ifixit.com were clear and helpful.

After installation, I discovered using System Information that the SSD in the CD bay had a negotiated link speed of 1.5 Gigabit rather than 3 Gigabit. So I opened up the MacBook Pro again and swapped the hard drive and the SSD. Next time I booted both drives were running at 3 Gigabit. As a temporary measure for testing, I formatted the SSD using Disk Utility as a single journaled HFS+ partition.

To create the Fusion Drive, I booted into the recovery partition by holding down Command-R during boot. I used the Terminal in recovery mode to create the Fusion Drive.

The first step was to use the diskutil list command to get a complete list of the partitions on both drives. In my case, disk0s2 was the partition on the SSD and disk1s2 was my usual Mountain Lion partition on the hard disk.

Then I used the command diskutil cs create Fusion disk0s2 disk1s2 to create a logical volume group from the two partitions. This is the step that was special. By specifying partitions rather than whole disks when creating the logical volume group. I was able to leave the recovery and Boot Camp partitions intact. Most instructions I've seen have used disk names rather than partition names, which wipes the entire disk clean. The use of partition names is documented in the diskutil man page.

Next I used the diskutil cs createVolume <ID from above> jhfs+ Reliance '100%' command to create a logical volume using 100% of the logical volume group. Since I still had my recovery and Boot Camp partitions, there was no need to leave room for them in the logical volume group, so I was free to use all of the space for my new Fusion Drive partition.

At that point the hard part was done. I booted from my cloned backup and used the Install OS X Mountain Lion application to re-install Mountain Lion on the Fusion Drive. (I could have cloned it back instead, but I liked the idea of taking the opportunity to reinstall Mountain Lion.) Once the install was done, I used Migration Assistant to copy my files and accounts from the clone back to the Fusion Drive.

As usual after a backup/restore, my Mac was busy for many hours re-indexing Spotlight and the next Time Machine backup was extremely slow. But once these things were out of the way, everything sped up and I started getting the benefits of my new Fusion Drive! It is continuing to get faster as it learns which applications I use most often.

There are a few glitches at the end of this process, but I consider them all extremely minor:

  1. If I boot with the option key down, my Mac firmware lists the Fusion Drive twice. Selecting either drive boots just fine.
  2. Disk Utility shows my Boot Camp partition as being part of the Fusion Drive, even though it is only on the hard drive. This seems to be harmless.
  3. The Boot Camp control panel in Windows 7 also lists the Fusion Drive twice. Again, both choices work fine.
  4. The first time I booted into Windows 7 I got the Windows boot loader screen, probably because I moved the hard drive with the Boot Camp partition to the CD bay. Windows 7 adjusted the drive address and it's been booting normally ever since.

All in all, it's a great upgrade and I'm glad I did it!

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    Stuart, now that it's been a few months, how is it working out? – Dan Pritts Feb 26 '13 at 17:25
  • How did you discover the negotiated link speed of your drives? – Jim McKeeth Apr 23 '13 at 17:54

In addition to @jtbandes being right, you can create and manage logical volumes using CoreStorage, but according to the KB Article HT5446 there are some "limitations" to the Fusion drive.

An alternative to the Fusion drive (which is basically a SSD AND an HDD grouped as a logical volume) is move the "/Users" folder to a HDD and leave all the OS X files and Apps in the SSD, you would get the SSD performance for apps and the OS, and all the space you need for your files in the HDD. Restoring from Time Machine on a different machine or reconfigured drive setup will not work with a moved /home for that user account.

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    To free up even more space, I would add /Library/Application Support /Library/Developer /Library/iTunes to the HDD as well. – dhempler Oct 26 '12 at 14:30
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    @dennis.hempler I agree completely! My '/Library/Application Support' is huge! Mainly because of Garageband tutorial vídeos, loops, and instruments. How can I move this folders to another HDD and link it to the SSD? Using Symbolic Links? Migration Assistant App? – dijeferson Oct 26 '12 at 15:38
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    Good comments - I for one am most interested in how the auto handling of tiered storage works so I don't have to choose what files go on what drive. – bmike Oct 31 '12 at 16:01
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    This would be a good answer to a different question, but not this question. The opening poster wants a single logical volume, with the system automatically moving frequently accessed data. – Graham Perrin Nov 3 '12 at 5:26
  • symbolic links will do what you want. Another thing to look out for is your itunes folder in your home directory. This is potentially huge even if you don't have a bunch of songs or videos - iphone backups go here. – Dan Pritts Feb 26 '13 at 17:26

I set up a Fusion drive using the Terminal utility in the OS X 10.8.2 installer loaded onto a USB thumb drive, after installing an SSD drive as the second drive in my 2011 Mac Mini.

This wiped out the data on both drives, but that's what I wanted: a fresh system with a new Fusion drive.

If you don't want to save your existing installation, just use the OS X 10.8.2 installer to create the drive (make sure it's 10.8.2 and above, though, as Fusion wasn't supported in 10.8.1 and earlier).

Once the installer had loaded, you can open a Terminal window and type in the diskutil commands there. Seemed easier to me than cloning my original drive to an external disc, booting from that, and Fusing the two drives.

The most complete and easiest guide I've seen written for creating a Fusion drive (and the one I successfully used) is at http://blog.macsales.com/15617-creating-your-own-fusion-drive.

Incidentally, if you have a 2011 Mac mini and haven't already bought the cable you'll need to connect the second drive, OWC has a great DIY kit. It's cheap, comes with a set of tools and glossy, professionally written step-by-step instructions. I was impressed. Available at http://eshop.macsales.com/item/OWC/DIYIMM11D2.


Here we made a video that outlines the process for you : http://www.youtube.com/watch?v=I_odnNpv-FQ

Commands you'll need in order:

diskutil list

diskutil cs create Fusion diskx diskx

NOTE: You can replace Fusion with whatever you'd like to name your Logical Volume Group

diskutil cs list

diskutil coreStorage createVolume YOUR_DEVICE_ID_HERE jhfs+ "Macintosh Fusion" 100%

NOTE: You can replace "Macintosh Fusion" with whatver you want to name your drive. Remember to use ""s if you want a space in your name like we did, otherwise you do not need them.

After installation is finished, open terminal and turn off indexing:

sudo mdutil -i off

If you would like to revert back to 2 separate drives, boot into the installer again, open Terminal and type:

diskutil cs delete YOUR_DEVICE_ID

You will then be able to format them however you'd like using Terminal or Disk Utility.

  • Is turning off spotlight mandatory or are you mixing in anger general preference. If you explain how your answer diverges from the prior answers (even if you are just trying to document things more thoroughly) it helps others use the content here. – bmike Nov 5 '12 at 17:59
  • While it is perfectly acceptable to add another answer it is preferable to add additional content/informations as well. – nohillside Nov 5 '12 at 18:01

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