Connecting Thunderbolt 3 vs Thunderbolt 2 Drive To New iMac

Discussion in 'iMac' started by 1957GoldTop, Aug 27, 2017.

  1. 1957GoldTop macrumors newbie

    Dec 8, 2012
    I just bought the latest 5k iMac. For a drive that I will be connecting to it, I was looking at the Promise Pegasus3 R6 (Thunderbolt 3) but found the Promise Pegasus2 R6 (Thunderbolt 2) for about $1000 less. Would I see any advantage from a Thunderbolt 3 version than the Thunderbolt 2 version? Isn’t the limit the drive speed, not Thunderbolt?

    I read that 5k monitors need Thunderbolt 3 speeds, but this doesn’t apply here since the iMac is both computer and monitor… this would only in matter if I wanted connect an external 5k monitor to the Pegasus, correct?

  2. propower macrumors 6502a

    Jul 23, 2010
    I believe you are right that Drive speed is the limit not TB. For 4 bay SSD drive RAID arrays I think ~1400MB/s is the limit. That is ~10,000Mbps (depending on overhead) and is 1/2 TB2 BW. Devices like the R6 are more for huge capacity AFAIK - ie RAID arrays of Spinning Drives that will be much slower. I am assuming you need fairly huge amount of storage with at least decent speed. For my more modest needs I am all SSD and use the AKITIO Thunder3 4 bay (Thunderbolt 3) unit.
  3. bergert macrumors regular

    Jun 24, 2008
    I would get the Pegasus3 unit in any case:
    1) P3 has different firmware - more features (P2 maxes out at 6TB, P3 supports 12TB disks)
    with the different firmware there may be other differences as well
    2) P3 uses USB-C (aka Thunderbolt3); but you can use an adapter - the speed of the Pegasus is not an issue: only with SSD disks it reaches 15GB/sec and exceeds TB1 speed. USB-C is a smart choice as it's future proof, will be around some time.
  4. theluggage macrumors 68040

    Jul 29, 2011
    Correct. And the iMac has 2xTB3 connectors so if you did add a 5k you wouldn't need to daisy chain it to the disc drive. Obviously, though, if you did want to chain multiple TB devices, TB3 has more bandwidth to go around and is going to be more "future proof" - but then $1000 is $1000...

    USB-C is not "aka Thunderbolt 3". Thunderbolt 3 (the protocol) uses USB-C connectors... so do a lot of newer ports that use USB3.1, USB2 and/or DisplayPort protocols but can't talk Thunderbolt and are (whatever the pedantically correct usage may be) typically described as "USB-C drives/docks/ports" etc.

    Oh, and the "-C" in "USB-C" stands for "Confusion" :)

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3 August 27, 2017