External SSD for 2017 iMac: TB3 or USB-C?

Discussion in 'iMac' started by bostich, Jun 15, 2017.

  1. bostich macrumors newbie

    Nov 4, 2012
    I'm still having a hard time understanding all the new connector types for external gear. Anyway, I need an external SSD for audio recording to connect to a new 2017 iMac at our studio. And I'd like it to be as fast as the internal SATA3 SSD I have in my Windows PC, if possible.

    So what's the difference technically between an external SSD labelled "TB3" (like the LaCie d2 TB3) and one labelled "USB-C" (like the Samsung T3)? I only know they use the same cable.

    Does the Samsung benefit somehow from being connected to a TB3 port, or does it behave just the same as when connected to a USB-C port on a PC? And what's the real-life speed difference between a TB3 SSD and a USB-C SSD connected to the iMac's TB3 port?
  2. tich macrumors member


    Mar 8, 2012
    Los Angeles, CA
    Either will work, but they are not the same. The only thing that's the same about them is their connector.

    USB-C has a maximum throughput of 10Gbps, Thunderbolt 3 is 40Gbps, and SATA3 is 6Gbps. So in theory, Thunderbolt 3 is much faster, however keep in mind it ultimately depends on the speed of the drive itself to take advantage of that extra bandwidth.

    AFAIK, the LaCie d2 TB3 you refer to only comes as a hard drive, not an SSD, so it will be slower than the Samsung SSD that's over USB-C because the of the spinning disk being the bottleneck. LaCie quotes 240MB/s for the d2 TB3, and Samsung quotes 450MB/s for the T3.

    USB-C devices will work in Thunderbolt 3 ports, but not the other way around. The Samsung will operate at the same speed on a TB3 port as it would on a USB-C port.

    Thunderbolt 3 requires a Thunderbolt 3 cable. USB-C cables will NOT work.

    Hope that helps
  3. bostich thread starter macrumors newbie

    Nov 4, 2012
    Thanks. That means an external USB-C Samsung T3 connected to a USB-C or TB3 port should be faster than the internal Samsung 850 Pro SSD I have in my PC?

    Are there any reasonably priced 1000 GB TB3 SSDs on the market? All I could find is a ridiculously expensive device from LaCie.
  4. campyguy macrumors 68040

    Mar 21, 2014
    Portland / Seattle
    Not yet, but the T3 might be dropping soon. Sammy's existing SSDs are on sale at Newegg and Fry's lately, and my vendor dropped me a link that the T5 should be out soon - it's from his company and I don't want him in hot water, but I did link in these forums earlier this week to a Korea Herald post from late May offering that Samsung would be ramping up for the T5 (I think that BGR posted that link as well. Sales on the T3 should follow…
  5. Fishrrman macrumors G5


    Feb 20, 2009
    For audio, a "regular" USB3 SSD will be plenty fast unless your needs are unusually demanding. You should see reads around 430mbps and writes from 250-350 (or higher, depends on drive size, model, mfr).

    If you want -more speed-, you might look for an SSD (probably will not be 2.5" form factor) in a USB3.1, gen2 enclosure. I believe these are touted to support speeds up to 10gbps. In the real world, I would expect reads @ 700-800mbps and writes of better than 500mbps.

    I wouldn't bother with thunderbolt for a non-booting external drive.
    Perhaps for video, but not for audio...
  6. epca12 macrumors regular

    Jun 11, 2017
    Couldn't you go for regular USB A 3.1? The iMacs support gen 2 so should be same speed as a type C drive but more free ports
  7. dborod macrumors regular

    Jul 22, 2002
    One other data point to consider... TRIM support is provided by macOS for TB3-connected devices, but not for USB-connected devices. To what extent this matters at all is a debated point of contention (see https://forums.macrumors.com/threads/boot-from-osx-external-ssd-thunderbolt-or-ubs-3-0.2050455/ ). This is also complicated by the fact that some drives do TRIM themselves, as to some controllers in external enclosures. I don't know enough of the details of this to advise you, but searching through these forums might yield something useful.
  8. thedeske macrumors 6502a

    Feb 17, 2013
    Reading about that as well. People are guessing 800 plus speed in a 3.1 gen2 port. Might be a nice single drive solution. The T3's still not bad at all.
  9. Taz Mangus macrumors 68040

    Taz Mangus

    Mar 10, 2011
    I think you are confusing garbage collection with TRIM.

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