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Creating a Fusion Drive for your Mac

I’ve been running a home made Fusion Drive on my MacBook Pro (mid 2012) for a while know, and it’s been rock solid under OS X Mountain Lion. But as a developer, and with access to Mavericks, I’ve been running the latest couple of beta’s on this machine. At first everything ran fine, but since beta 4 the machine started acting up. Sleep/Wake resulted in Kernel Panics, booting with Option made the boot drive appear twice, and the machine runs either at fast SSD speed, or is slow as hell. And did I mention spotlight re-indexing every couple of days, Dropbox thinking I’ve reinstalled it once again, CrashPlan uploading whole systems again? Trust me, upgrading a home-brew Fusion Drive from Mountain Lion to Mavericks is not stable at all.

While reading through the Developer notes, I saw this lovely note appear:

Finally, the notes point out that Fusion Drive volumes created in Developer Preview 3 are incompatible with OS X 10.8.4 or earlier - Apple Insider

Reading between the lines, I think Apple changed something in how they handle or build Fusion Drives with Mavericks. Since the lack of a Recovery Partition on my current installation also made FileVault and Find my Mac do weird things, I decided to start from scratch and rebuild my entire setup.

The result I was going for:

Preparations

What you need

External Installer

Creating the Fusion Drive

Creating a Recovery Partition

On our new Fusion Drive we’re going to want a Recovery Partition. Since a Fusion Drive is a CoreStorage volume, it can’t be resized after its creation so we need to make room for the Recovery Partition before we create the CoreStorage volume.

This guide assumes you’ve got your two drives already installed. Go to iFixit if you don’t know how

Option A: I'm currently running a Fusion Drive.

Option B: I currently don't have a Fusion Drive and have a Mac with a working Mavericks Recovery Partition on an HDD

Option C: I currently don't have a Fusion drive and have a Mac with a working Mavericks Recovery Partition on an SSD

Merging the drives

We now have a Mac with two drives and a working Mavericks Recovery Partition on the HDD. All that’s left is fusing them together.

Creating the Logical Volume Group

Formatting the Fusion Drive

We’ve now merged the two parts together, but it’s still invisible for our file system to work with. In order to get data on the drive, we need to format it.

Finishing up

I hope Apple creates an officially sanctioned way to make Fusion Drives, and builds into the Recovery Partition. But in the meanwhile, I hope you enjoyed this guide.

And please always: backup, backup, backup. And I’m not responsible for any data loss.

Questions? Remarks? Contact me and I’ll try to answer them with updates to this article.