More on DIY Fusion Drives

Understanding of the ins and outs of OS X's CoreStorage will come into play with the making of a home-brew Fusion Drive.
Written by David Morgenstern, Contributor

The latest guide to creating your own Fusion Drive can be found in the January cover story of MacTech Magazine, which is available only in hardcopy on store shelves or via electronic subscription. The article titled About the Fusion Drive by Gary Alevy is filled with useful information and tips on the process of making a Fusion Drive from scratch.

Alevy points out that so far, management of a Fusion Drive is all about the Command Line.

At the time when this article was written, the graphical user interface version of diskutil could only display basic information about a Fusion Drive such as its capital Name, Mounted Logical Partition, Logical Volume G (LVG), and Mount Point. There was no graphical user interface program for managing the fusion drive.

If you're interested in the details of the CoreStorage commands, take a look at Stephen Foskett's Pack Rat blog, where he has the list of documented and undocumented CoreStorage commands.  If you are braving the making of a Fusion Drive, I also suggest that you look at Fosketts' multipart series on CoreStorage (even though it was written at the release of ColdStorage in OS X Lion). 

Alevy presents a useful list of limitations of the Fusion Drive, including that the SSD used in the scheme can't be partitioned and that the hard drive used in the setup can only have one or two partitions. The list goes on and any of these considerations must be weighed before continuing. Undoing everything will take some doing.

Check Out these Apple Core Fusion Drive stories:
Please stop the madness: The Mac's Fusion Drive isn't about caching
DIY Fusion Drives not for the timid

One of the more important considerations is software compatibility. Before purchasing a machine that comes preconfigured with CoreStorage volumes or a Fusion Drive from Apple, check out the compatibility of your software, especially mission critical applications.

There are a number of applications that don't support the Fusion Drive or even CoreStorage and some are used in enterprise environments. One such I discovered recently is Faronics' Deep Freeze deployment software. It's software that deploys a "desired configuration" of software on the Mac and won't accept changes or additional software after a work session. Once restarted, it reverts to the standard config. Data is stored in a safe Thaw Space, the company said.

However, a recent Faronic support note pointed out that Deep Freeze doesn't support a CoreStorage machine, nor a Mac with a Fusion Drive. Now, it's possible to remove the CoreStorage volume and reinstall OS X. However, there's no workaround for a Fusion Drive machine, the company said.

Alevy made it sound as if many hurdles had been overcome in making home-brew Fusion Drives. Yet, I still read of problems in discussion boards. I didn't have the time or the will to try it out this winter vacation. Maybe in the spring. If you've got one working, please let me know.

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