External SSD boot - USB or Thunderbolt?

Discussion in 'Buying Tips and Advice' started by dpfenninger, Jun 1, 2014.

  1. dpfenninger macrumors regular

    Nov 23, 2005
    I'm looking to get a new iMac, but would like to use the SATA SSD from my old MacBook in an external enclosure to use as a boot drive (and maybe even make it part of a Fusion drive coupled with the internal hard drive). Anyone have a suggestion for whether to go USB 3.0 or Thunderbolt with the enclosure? USB would definitely be much cheaper, but I've heard about issues with CPU overhead using a USB enclosure in such situations; Thunderbolt is faster (and wouldn't impact CPU usage?) but the cheapest enclosure I've found that you can add your own bare drive is this one, still way pricier than USB.

  2. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    The speeds of USB3 and TB are very close. See this test. If you go with USB3, make sure you get an enclosure that supports UASP like this one.

    UASP reduces the processor overhead, so that is not really a concern.

    The advantage of TB is it supports TRIM where USB does not.
  3. dpfenninger thread starter macrumors regular

    Nov 23, 2005
    Thanks for the info! I should mention too that this is the SSD that I will be using...an older model that USB 3.0 will have more than enough bandwidth to handle, and should still give a significant speed boost over the stock internal HD.

    Now...I'd really like to do a homemade Fusion drive with this combination. Hopefully I'll still see speeds comparable to a separate SSD/HD two-drive setup.

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