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Mac Mini: Dual Drives Are Better than 'Fusion'

2012 Mac Mini 2.3 GHz quad-core, 16GB OWC memory, 240GB OWC Extreme Pro 6G SSD.

The 2012 MacMini can take dual internal drives.

Apple will also sell you a MacMini with dual drives with OS X server (not my preferred choice). Or you can build your own setup.


Apple wants $250 more for the Fusion option. This is not a good value versus the alternatives as discussed here.

Let’s cut to the chase on what you can get for your money.

- Prices at time of writing, click the links to see current prices.
- Mercury Electra 6G SSD cost is somewhat less than the Extreme Pro 6G.

The 'Fusion' option isn’t a huge value and it actively reduces the robustness, reliability and versatility of the Mac Mini versus two separate drives. But it is a single supported solution that will appeal to many users not looking for anything more.

  Apple Fusion Separate SSD + HDD
Cost + $250 240GB OWC Extreme Pro 6G SSD + OWC Data Doubler + toolkit = about $330

480GB OWC Extreme Pro 6G SSD + OWC Data Doubler + toolkit = about $629

(OWC will install memory and drive as a service).
Options NONE 120GB or 480GB or 960GB options
Guaranteed speed for critical tasks NO YES
Capacity of SSD 128GB
(but maybe only 120GB usable, as per past Apple SSD options)
240GB (or more)
Separate Boot drive NO YES
Internal clone NO YES (on HDD)
Internal Time Machine NO YES (on HDD)
Upgradeable SSD NO YES, just backup and clone/swap
Upgradeable HDD NO
(at least not easily)
YES, just backup and clone/swap
Works with disk repair tools Maybe, maybe not (according to Apple) YES
Reliability Failure of SSD or HDD means TOTAL FAILURE Failure of one drive fails only that drive, the other remains intact
Serviceable by user? Considerable “nerd” skill required to deal with Fusion volume setup (if failure) Simple conventional single drive initialize/format
Can be partitioned? One partition only, Fusion benefits are lost on the 2nd partition YES, either or both drives
Special Disk Utility needed? YES (“earlier versions cannot be used”) NO
Extra disk activity and thus increased noise and power consumption? YES— when files are moved around in the background NO

Other considerations

See Does Fusion Actually Migrate Files?.

Videos and music

There is no benefit to keeping video clips and music on a fast drive; their streaming rates are very slow. So if you watch the same video or listen to the same music repeatedly, chances are the Fusion SSD will waste its capacity for no benefit.


The Fusion volume will spin up the hard drive when used. With two separate volumes, the hard drive can spin down unless actually in use, even if the separate SSD volume is being used.

Scratch disk for Photoshop users

For Photoshop users, there is no way to say “use the SSD for scratch”, since it is hidden from usage. But since Fusion keeps a 4GB buffer for writes, SSD speeds will be available for files that are not too large.


With Fusion, one cannot guarantee that the catalog folder will reside on the SSD, yet this is critical for peak performance especially in Lightroom “Library” mode (scanning through files).

Complexity and reliability

While it might engineered to high standards and be highly reliable, two drives fused into one volume cannot be as reliable as a single drive or two separate drives/volumes, because failure of either drive fails the volume.

If nothing else, two drives / two volumes means that there are “two baskets for eggs”, not all eggs in one basket.

A better approach: two drives / two volumes

Most work scenarios involve a need for performance with some data / files.

All work scenarios require backup, preferably at least two external backup drives stored elsewhere, like the OWC Mercury Elite Pro. Having Time Machine connected to or internal to the machine is a big plus for everyday use, but should not be construed as adequate on its own— external backups are essential.

Benefits of two separate internal drives

Here are just some of the benefits possible, assuming an SSD + HDD (hard disk drive) combination.

Assume the SSD is the volume Boot, and the HDD is the volume HDD.

  • The system, applications and anything needing guaranteed fast I/O can reside on Boot, which is always fast, all the time. A typical system with many applications is only ~45GB total, so it fits easily onto even a small SSD.
  • Photoshop scratch, Lightroom catalogs, caches of various kinds and any disk-speed-sensitive items can live on Boot. Thus, the fast SSD speed is guaranteed 100% of the time for these important tasks.
  • The HDD can be used for storage of bulky items. Large image RAW files can reside on HDD, as can music, videos, etc. Music and videos have very low data rates, and RAW image files (e.g. for Lightroom) are not a significant speed factor either.
  • Large Photoshop files (500MB or larger) can be saved on Boot while being actively edited, then moved over to HDD when the job is done. Thus one gets guaranteed speed when it matters.
  • The HDD can be partitioned to include BootClone (a clone of Boot), with space left over for extra storage. Alternately, the HDD can be used for Time Machine or other purposes.
  • The HDD can be replaced with a larger one when and if needed, without affecting anything on Boot. And vice versa.
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