Creating the Fusion Drive the way these walkthroughs say (including OWC's exceptional guides), destroys the Recovery Partition that exists on the drive. Without a Recovery Partition, you cannot enable FileVault2, and will need some other external boot drive if you ever need to perform maintenance on your internal drives. For a laptop computer that might be far from home, not having a Recovery Partition was unacceptable to me. Also note that if you buy a Mac from Apple today with Fusion Drive, it DOES come with a Recovery Partition, so it is indeed possible to do.
It turns out that Apple's Core Storage technology is more flexible than these walkthroughs give on. You can enroll an individual partition of a drive in a Fusion Drive, instead of the whole drive. This means that you can join just a specific data partition of your HD with an SSD, and leave the Recovery Partition intact.
I've created a Fusion Drive (SSD + Original HD), that HAS a Recovery Partition, and is now encrypted with FileVault2. It is a lot faster than the original, so I'm calling it a success.
Steps to reproduce:
- Make a bootable clone to an external disk (using SuperDuper or CCC).
- Boot off the clone drive, make sure it's good. (Hold down the Option key when booting for a menu of available boot disks)
- Shutdown. Install the SSD per OWCs excellent install videos. I used OWC's 'Data Doubler kit,' and am quite happy with it.
- Boot off the clone again.
- Run Terminal.app.
- Determine your disk ID's by typing
diskutil listat the prompt. - The SSD will likely be disk0. The original HD will likely be disk1. Partitions on the HD will likely appear as follows below.
- Note: The trick is to enroll just the data partition of your HD into the Fusion Drive, and not the whole disk. Next step does that by enrolling 'disk1s2' (the data partition), instead of the whole disk ('disk1'). All the walkthroughs say to enroll the whole disk ('disk1'), and that is the major way we are diverging here.
- Issue the following Terminal command:
Note: [ArbitraryName] should have spaces and special characters escaped. I used 'Fusion,' to avoid any special characters, so I couldn't mess up.
sudo diskutil cs create [ArbitraryName] disk0 disk1s2
- Caution: The step above will wipe all data from your data partition disk1s2. That's an unavoidable step in the process, and is why we made a bootable clone first.
- The final output of the previous step returns a UUID (ex., 352D9D2B-E0F2-4A16-B583-A257802EC74C) for your new CoreStorage volume. Copy that to your clipboard.
- Issue the following Terminal command:
Note: [ArbitraryDriveName] should have spaces and special characters escaped. I used Macintosh\ HD. You can always use something simpler, and rename the drive later in the Finder.
sudo diskutil cs createVolume [paste the UUID here] jhfs+ [ArbitraryDriveName] 100%
- Copy the contents of the external clone back to the Mac (using SuperDuper or CCC) again.
- Reboot, from the internal hard drive (fusion drive, yeah!). Disconnect the external drive. Don't erase the external yet, in case something went wrong.
- Test that your Recovery Partition still works (it should), by rebooting with Command+R held down. Do the recovery tools load? If so, then it is a success!
- Reboot to normal internal HD. Does everything look fine? If so, then now you can activate FileVault2.
- Assuming no problems have occured, NOW you can erase your external temporary clone.
disk1 GUID_Partition_Scheme disk1s1 EFI disk1s2 Apple_HFS - This is your actual data partition (typically 'Macintosh HD') disk1s3 Apple_Boot - This is your Recovery Partition
The hint is pulled from the MacOSXHints forums site, here. The step-by-step instructions are contained in post number eight of that thread.
[crarko adds: I don't have the hardware to try this out. If I did do this, I would probably keep the cloned boot drive around a few days, just for paranoia's sake.]

