I want to buy external RAID 2.5" drive. I am looking at Lacie Rugged RAID Pro: https://www.lacie.com/www-content/datasheets/pdfs/rugged-raid-proDS1975-2-1805US-en_GB.pdf

They state, that it can only be bus powered via Type-C cable. The drive itself has Type-C connector, and includes Type-C to Type-C and Type-C to Type-A cables.

I wanted to confirm if my understanding is correct, that you simply need USB3.1 Gen 2 port on your computer to be able to power it - it does not matter if the computer port is Type-C or Type-A?

Or am I misunderstanding something here, and all Type-C ports on computers are somehow inherently higher powered?

Thank you.


As far as I understand it, with version 3.1, the specification was split into "USB 3.1 Gen2" (data signal) and "Type C" (physical cable and connection).

  • USB Type-C specifically allows up to 1.5A for "standard" ports (and 3A for "charging" ports).
  • Meanwhile, Type-A connections – whether they use 3.1Gen2 data signalling or not – retain the same USB 3.0 limit of 0.9A for normal ports (1.5A for charging ports).

Based on the name and reviews, the "Rugged RAID Pro" has two 2.5" disks inside (otherwise it couldn't very well call itself a "RAID"), and likely a more power-demanding disk controller as well, so you're looking at more than twice the power requirements of a normal 2.5" disk. It could be that it just barely fits in 0.9A but would work unreliably.

(For comparison, USB 1.0/2.0 had a limit of just 500mA.)

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  • Do you have any references? I was always under the impression that "Type-C" simply denoted the connector and it doesn't make much sense to me that the wiring inside the MB would be different for different port types of the same spec level. But, of course, a lot of strange things have already happened, so it might aswell be true. – mrQQ Feb 18 '19 at 7:20
  • Not offhand, but the type-C connector is in a way a different "spec level" all by itself, as it already deals with new wiring (alternate modes); it's not in any way unusual. – user1686 Feb 18 '19 at 7:40

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