The effects of fission on Fusion drives

June 13, 2015 12:14 PM

In hopes of getting another couple good years out of my 2011 Mac mini, I'm planning to do the DIY Fusion Drive thing -- formatting the stock HDD and an SSD drive as a single logical partition. Currently my plan is to keep the SSD in an external FireWire enclosure, with the possibility of installing it inside the Mac mini further down the road if I can get over my fear of hardware.

So the question is: Will mounting the external/Firewire SSD as an internal/SATA drive require me to wipe everything and start over further down the line? Will I be entering a world of pain if I try to do this in stages, or will OS X be smart enough to take the changes to the logical volume in stride?

posted by bokane to Computers & Internet (9 answers total)

Best answer: This sounds like a lot more work and risk than necessary, especially given that you won't get nearly full performance out of that SSD over FireWire. Make a full Time Machine backup, install the SSD internally, make a clean install of OSX to the SSD, then restore from the backup. You want your fast data on a fast connection, while your long term storage can be external.
posted by fifthrider at 1:44 PM on June 13, 2015 [2 favorites]

Response by poster: Thanks for the reply! And looking around, it seems like leaving the two as separate drives might be preferable to formatting them as a single volume anyway.
posted by bokane at 2:32 PM on June 13, 2015

Best answer: Yeah; it's like yoking a horse to an ox: the ox won't go much faster, and if one trips they both break a leg.

That said, remembering to store things on an external can be a drag, so if you're sure that your external storage will be connected all the time, you can put your home folder on that volume, while the rest of the system lives on the SSD. Here's a guide. I've only ever done this on Linux, where you do it a different way, but I think this process should serve.
posted by fifthrider at 2:38 PM on June 13, 2015

Just one heads up.
I had trouble with a OWC 6G Electra in my 2012 Mac mini. Ended up using a normal HD.
Never had this on any other Mac with either Samsung or OWC SSD drives.

My advice; Mac out the Memory to 16GB. Install a new fast drive (WD Black label) do a clean install and call it a day.
posted by Mac-Expert at 4:45 PM on June 13, 2015 [1 favorite]

Response by poster: Thanks for the warning. I've already maxed out the RAM in the 2011 mini, so the drive is the only thing left to soup up. I got a deal on a Samsung SSD, so will probably try my luck with that, and revert to the Old Bad drive if things go south.
posted by bokane at 5:28 PM on June 13, 2015

If your Samsung SSD is 9.5 mm or thinner then I'd recommend looking at OWC'd "data doubler". It stacks the SSD on your HDD internally.

I did this on my 2012 mini last year and install was painless.

Booted from Mavericks install on a USB stick, went to terminal before install and created the fusion drive, installed the OS and restored from back up.
posted by alamedarchy at 6:15 PM on June 13, 2015 [1 favorite]

Response by poster: Yup - I've ordered iFixit's drive doubler kit, which as far as I can tell is the same as OWC's. The installation videos I've watched seem a bit intimidating, but I think I've probably got about a 75% chance of not bricking my mini in the process.
posted by bokane at 6:43 PM on June 13, 2015

One last thing - if you're using a non-Apple SSD, make sure you look up how to enable TRIM support for it on your version of OSX. Apple keeps playing games with that.
posted by fifthrider at 9:57 PM on June 13, 2015 [1 favorite]

Response by poster: Word. I'd seen some mention of that online, but wasn't sure whether or not it was still an issue.
posted by bokane at 8:00 AM on June 14, 2015