Luke Christian
Level 1
(25 points)
Q: Create Fusion Drive for Mac Mini?
With the falling prices of SSDs, I am fascinated by the prospect of adding one to my Late-2012 quad-core i7 Mac mini and set it up as a single Fusion Drive volume with the existing 1TB HDD.
The clunky 5,400rpm HDD that it came with is laboriously slow and the opportuity to add a 256GB SSD (probably a Sandisk?), for a lot less than the incremental price hike of having specified a 128GB Fusion Drive in the first place, seems very tempting. Better still, it was mentioned, in another thread, that Disk Utility in later Mac Minis automatically set-up two installed drives as a single Fusion Drive volume, so I would not even have to delve into the dark arts of the Terminal to set it up, just pick-up a disk doubler kit from iFixit or OWC, drop in the SSD, load OS 10.9 onto the SSD, boot into Disk Utilities, select 'Repair Disk' then go and make a cup of tea!
Even though I might have to forfeit my remaining 6 months of Applecare, it seems like a compelling way to vastly improve my Mac mini's disappointingly sluggish performance. I always back-up to Time Machine so am not overly concerned about doubling the risk of data loss with a Fusion set-up.
It all seems too alluring... am I missing something?
Can someone temper my enthusiasm before I bite off more than I can chew with a perfectly good 6-month-old Mac mini?
Mac mini, OS X Mavericks (10.9), rMBP, 2x 24" LG monitors.
keg55
Level 6
(8,514 points)
You don't need to use Terminal commands with OS X Mountain Lion 10.8.2 and above (which includes OS X Mavericks). You can create your Fusion drive by restarting into the Recovery HD (Command+R). Then launch Disk Utility. You will see both drives marked in RED lettering and a popup will display giving you an option IGNORE or FIX. Clicking FIX will erase both drives and automatically create a Fusion drive. So, do a full system back up before creating a Fusion drive.
In case you want to use the SSD and HDD separately, know that in Disk Utility from the Recovery HD in OS X Mountain Lion there's a bug with the IGNORE/FIX buttons. The IGNORE will do nothing and won't let you individually manage each drive. You would have to use Terminal (diskutil) to manage them. In OS X Mavericks, that bug has been fixed and clicking IGNORE will change the RED lettering to black and let you manage each drive separately.
TRIM aids in the reduction of write amplification and some improved performance. A 3rd party free app called Trim Enabler will enable OS X's TRIM feature on 3rd party SSD drives.
This produces three key benefits:
- Lower write amplification. Less data is re-written and more free space is available during GC (more space to write equals fewer writes needed);
- Higher throughput. With the TRIM command, there is less data to move during GC and the drive runs faster. Throughput is bottlenecked at the flash an SSD is only as fast as it can write to the flash memory. During the time it is doing GC, the drive has to stop some of the data transfer from the host while it moves data around. This is why it’s beneficial for the SSD to know which data is invalid so it doesn’t have to be moved during GC.
- Improved endurance, because the drive is writing less to the flash by not rewriting invalid data
I had a Fusion drive in my late-2012 Mac Mini (120GB SSD, 500GB HDD) and there was a definite performance improvement. I think it booted up in ~16 seconds compared to ~ 30 seconds without it and apps launched much faster. I've since "defused" the drives and have separate drives. Just a preference for me, but I didn't have any issues with a Fusion drive and I enjoyed the ease of file management which was done for me by Core Storage. I didn't enable TRIM on my 120GB SSD since I rarely do any deleting of files. Most files are deleted off my HDD which is used for LAN file storage. So the built-in Garbage Collection on my SSD is good enough.
