I need to connect two 4TB or, better, 5TB external drives to the free Thunderbolt 2 port on my late 2015 27-inch iMac, hopefully daisy-chaining these new external drives together so I can use just the one free Thunderbolt 2 port.

(The machine does have 2 free USB 3 ports as well, but I'm guessing that these would not be as amenable as the one free Thunderbolt 2 port for this proposed external drive expansion requirement.)

I'm not seeking brand recommendations here, just advice as to the possible connection protocols that will enable 2 5TB external drives to be connected to this single Thunderbolt 2 port - if they exist.

What would be the fastest drives/connections to do this, hopefully keeping the external drives bus-powered?

  • apple.stackexchange.com/questions/43827/… has some pointers, and there are other Q&A on this on the site as well. This doesn’t mean that your question will be fully answered by what you find, so feel free to come back with specific questions.
    – nohillside
    Commented Nov 26, 2019 at 15:42
  • the really helpful comments were unhelpfully deleted. Thanks.
    – nev
    Commented Nov 27, 2019 at 16:23
  • Comments should be used for clarifications, not for answers. @Allan, do you want to post your view on this as an answer below?
    – nohillside
    Commented Nov 27, 2019 at 16:55

1 Answer 1


I’m a big fan of using a dock or enclosure to reliably connect drives rather than chaining them. Cable chains can be safe and secure and work well, but I prefer one cable and hard mounting the drives:

Most basic enclosures work in JBOD mode since you don’t usually want to RAID / mirror less than 5 drives or without a nice controller for most uses.

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