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I prefer to keep my boot drive external, so that I can quickly boot using another Mac if my primary Mac fails. I use a USB3 drive dock to connect the drive to my Macs.

I bought a 120GB SSD w/SATA3 (6.0Gbps) interface, capable of pushing >500MB/sec read and 260MB/sec writes, sustained.

USB 3.0 is pretty fast -- spec'ed at 5.0Gbps. I'm thinking that performance over USB 3.0 should be at least in the same ballpark as SATA3 (6.0Gbps). It's about an hour of risky, careful work to install the SSD internally in my Mac Mini, is it worth it?

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Specs like data transfer speed often give a misrepresentation of real world performance of the interface. The latency on USB3 can be an order of magnitude higher than on SATA3, which makes a huge difference when your dealing with generally randomly access data (such as boot files, application files, etc.) – XAleXOwnZX May 22 at 22:17

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YES, it's definitely worth it. With my setup, sustained transfer speeds were roughly 75% better using SATA, vs. USB3.

I tested both configurations using ZoneBench as follows:

SSD: 120GB OWC Mercury Electra 6G

Mac: Late 2012 Mac Mini, 2.6Ghz core i7, model ID Macmini6,2, 16GB RAM

Hot-Swap unit: StarTech USB3-to-SATA dock, model SATDOCK22U3S ver2

  All speeds are in MB/sec (mega-bytes per second)

  Configuration A: SSD connected via Hot-swap USB 3 Dock
  Lowest / Avg / Highest R/W speeds:  95 / 150 / 185

  Configuration B: SSD installed in internal HDD bay in 2012 Mini (direct SATA):
  Lowest / Avg / Highest R/W speeds: 145 / 250/ 460

All tests were repeated 5 times at intervals of 1 hour, under normal system usage. (A few apps open & idle, CPU & system I/O load 99% idle.)

As one can see, in this configuration, taking the trouble to mount the SDD in the Mini's internal SATA bay is well worth the massive performance gains.

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I don't know about your mac mini, but my MBP thats a few years old I would have to also replace the cable from the SDD to the logicboard to get the most out of the SDD. It's unlikely the computer came with a cable installed intended to power a SDD given the price of that cable being a little higher. – Ryan Hollingsworth Jun 5 at 16:08
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It is worth it since you'll have your fast drive connected internally. Only in the case where you're worried about being able to boot off another server quickly, backup/clone your Mini to that USB3 drive would I keep the SSD externally connected.

The decrease in reliability of SSD vs. HDD can be countered by an automated backup system. You are doing backups, right?

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Can you add some details about why you think it's worth it? – patrix♦ May 24 at 3:30

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