Apple announced a new storage technology, called Fusion drive at an Apple Media event last October. Fusion Drive, which is available as an upgrade option in Built-to-order (BTO) iMacs and Mac Minis combines Solid State Disks with regular spinning disks, thus offering high performance and high storage capacity at the same time.
Apple describes Fusion Drive as:
Available as a configurable option at the Apple Online Store, Fusion Drive is a breakthrough concept that combines the high storage capacity of a traditional hard drive with the high performance of flash storage. With Fusion Drive in your iMac, disk-intensive tasks — from booting up to launching apps to importing photos — are faster and more efficient. That’s because frequently used items are kept at the ready on speedy flash storage, while infrequently accessed items go to the hard drive. The file transfers take place in the background, so you won’t even notice. As the system learns how you work, Fusion Drive makes your Mac experience even better. And you don’t have to do a thing.
I own a late 2009 27″ iMac that I upgraded to 16GB of memory and 2TB hard disk space. A couple of months ago I switched to a 512GB Crucial M4 Solid State Drive, but I quickly realized that 512GB are pretty tight. Then in October Apple announced Fusion Drive and made it available to newer iMacs and Mac Minis. Shortly after, I read that Patrick Stein aka @jollyjinx figured out that OS X 10.8.X supports Fusion Drive on older Macs as well, as long as you have both a spinning and a Solid State Drive connected via SATA.
So I decided to give Fusion Drive a spin by opening up my iMac and installing both the spinning disk as well as the Solid State Disk I already had.
Parts and tools
- Seagate Barracuda 2TB 7200RPM disk* (or the drive that you currently use with your iMac)
- Crucial M4 512GB Solid State Drive* (or any other size/brand or your liking)
- Suction Cup*
- Torx screwdrivers*
- 13 PIN F to 22 PIN F SATA CABLE*
- Any screwdriver
Before taking my iMac apart, I downloaded OS X Mountain Lion from the App Store on my MacBook Pro and copied it to a bootable USB stick using a utility called Lion Disk Maker. Despite the name, it also works with Mountain Lion.
To take out the motherboard of my iMac, I pretty much followed a guide by Brian Tobey – the only difference between his iMac and mine I discovered was that mine did not have a spare SATA connector, so I had to disconnect the optical drive (which I barely used anyway) to plug in the SSD SATA cable. Also, my motherboard layout was slightly different, but that was not a big deal. To make sure I could re-assemble the iMac, I took a picture of my motherboard before unplugging all connectors. I also mounted the SSD right under the optical drive and put everything back together. To my surprise, the iMac booted up right away – a sign that I correctly wired at least the major connectors :)
Next, I booted off the USB thumb drive by pressing the Options key during boot up and then selecting the thumb drive. That loads the Mountain Lion recovery environment. Once the recovery environment was up and running, I opened Disk Utility to confirm that OS X saw two hard drives, my 2TB Seagate Barracuda and my 512GB Crucial M4. Then I opened up a command shell to create a logical volume spanning both disks. I followed pretty much the guide of Patrick Stein with some minor exceptions.
On the command line I first issued the following command to figure out what disks I was dealing with:
diskutil cs list
In my case, disk0 was my SSD and disk1 my spinning disk. Then I issued the following command to create a logical volume spanning both disks – “blah” is just a dummy name and you can certainly choose another label:
diskutil cs create bla disk0 disk1
Then I ran another
diskutil cs list
And marked/copied the ID of the Logical Volume Group. It has the following format (but your ID will be different of course): DE85044F-EADA-4F26-93B7-8CD0ADF006EC
Next, I created an HFS+ volume using the following command (replace the volume ID marked in bold with the one on your system):
diskutil coreStorage createVolume DE85044F-EADA-4F26-93B7-8CD0ADF006EC jhfs+ blub 2500g
The label “blub” you can certainly change to whatever you want to and the 2500g (meaning 2500 GB = 2.5 TB) can be changed as well to match the combined size of your two disks. In my case I had a 2000GB spinning disk and a 512GB SSD – so I used 2500g in the command above.
If all the commands above executed without errors, you now have a 2,500 GB Fusion Drive. Last but not least, quit the Terminal and start the installer, which should now see only one available disk to install OS X on.
- Since I replaced the original Apple 1TB spinning hard drive with a non-Apple Seagate Barracuda, the temperature sensor connected to the drive could no longer sense the temperature correctly. This is a known issue caused by Apple using a different PIN configuration in its sensor cables. There are two workarounds for that – you either shorten out the sensor cable with a paperclip, or you buy a third party application that monitors the HDD temperature through SMART and controls the HDD fan accordingly. I opted for the latter by purchasing a copy of HDD Fan Control.
- I haven’t had time yet to perform IO tests, like the ones Patrick Stein has done but based on what I’ve seen so far, my IO performance is much better than it used to be with only the spinning disk.
- Taking out the motherboard of your iMac and installing an SSD may or may not void your warranty – I just don’t know. The fact is, that none of what you’re doing if you don’t damage anything, can’t be undone. So worst case, you put everything back to how it was before taking the iMac to the Apple Store (if it needs repair).
Thanks to Patrick Stein and Brian Tobey for their articles! Let me know if you have any questions or issues.