The difference is startling
I immediately saw an enormous difference, as if I'd swapped the computer rather than the startup disk. The FireWire 800 bus is clearly fast enough to make the difference for the kind of reading and writing that was occurring. Restarting the first time, in which OS X was clearly engaged in some cleanup and caching, took about six minutes. Subsequent restarts are in the two- to three-minute range.
The oddest thing I've discovered a few days in is that I'm seeing less use of memory. The maximum tops out at just above 11GB, when it used to approach 15GB or more. This is inexplicable and counter-intuitive. Why would faster storage result in more unused RAM?
After I was sure I had a clean backup of my boot drive, I changed SuperDuper to backup the SSD to the Mac mini's internal drive. In a pinch, should the SSD or its enclosure fail, I can boot off that internal drive with zero fuss — though I'd be back to the old, slow speed until I got the SSD fixed.
When I'm ready to upgrade my Mac next, whether to an iMac with Retina 5K or a next-generation mini, I've got a portable solution: I can buy a Mac with a cheaper hard drive or Fusion drive, and leverage this purchase over USB 3.0 to start out as zippy as possible.
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