Here is an interesting additional consideration on Thunderbolt vs. USB 3, as posted by a reader on MacInTouch:
"Feb. 24, 2015
Thunderbolt
Michael Skinner
Dirty secret on Thunderbolt: When setting up a new email server (Kerio Connect), we spec'd a Drobo Mini with four 512GB SSDs installed for the mail database. Had the option of connecting the Drobo via USB 3.0 or Thunderbolt. Decided to test both connections, and discovered something unexpected. USB was ever so slightly slower than Thunderbolt (given these SATA SSDs that could not leverage Thunderbolt's full potential), but CPU usage was much higher using Thunderbolt than USB 3.0. When copying a 7GB file, Thunderbolt was a few seconds faster, but idle CPU went down to 83%. Copying the same file over USB, idle CPU stayed above 96%. This was wholly unexpected, because it is the opposite of conventional wisdom regarding FireWire vs. USB. Who's have thought Thunderbolt would be such a CPU hog? Based on this, I rolled out the server with the Drobo attached to USB. I have been happy with the decision, the server rarely peaks 10% CPU even during intensive operations.
[I wonder if UASP (USB Attached SCSI) was at play here? -Ric Ford]"
