DIY Fusion RAM disk on a MacBook Pro

Summary:Back in the earliest days of Macintosh when storage meant floppy diskettes, RAM disks were all the rage. Now, a clever tip works a combo of new CoreStorage commands and Sparse Disk Images to create Fusion Drive RAM disk.

There's plenty of interest in the CoreStorage Fusion Drive technology used in Apple's recent MacBook Pro models. A number of blog posts have offered details on do-it-yourself Fusion Drives. As I've mentioned in previous posts , these projects aren't for the faint of heart when it comes to potential reliability. But some swear by them.

Here's a novel take in a blog post by Michael Logozar, who works by day building out large-scale messaging platforms for ISPs — meaning he's had some experience with tiered storage. He told me he was "intrigued" when he heard about the Fusion Drive and thought it could be applied to his music composition setup.

His brainchild is to combine the CoreStorage commands with Apple's built-in Disk Image virtualized storage containers.

This was all too risky for me, so I decided to try take it a step further. Borrowing a page from other virtualization technologies, I decided to try building a Fusion Drive out of disk images instead with the intent of benefiting from the speed of my internal SSD without having to rebuild my whole machine.

I did some re-arranging of my data to free up 128GB of space on my primary internal SSD and about 800GB of space on my internal HD and proceeded to build a Fusion Drive *without* reformatting my hard drives.

The post offers step-by-step instructions. However, there are steps where it's possible to make mistakes — serious ones.

Be very careful here to specify the correct disk identifiers or you could overwrite your main disks and cause severe data loss.

In the above example, it would be "disk5" and "disk6". Ideally you could run a "diskutil list" before attaching your disk images and one after to compare the difference to be certain.

Check Out: More on DIY Fusion Drives  

Topics: Apple, Laptops, Operating Systems, Storage

About

David Morgenstern has covered the Mac market and other technology segments for 20 years. In the recent past, he founded Ziff-Davis' Storage Supersite, served as news editor for Ziff Davis Internet and held several executive editorial positions at eWEEK. In the 1990s, David was editor of Ziff Davis' award-winning MacWEEK news publication a... Full Bio

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