Thunderbolt performance

Discussion in 'iMac' started by warrenl, Aug 20, 2015.

  1. warrenl macrumors member

    warrenl

    Joined:
    Jun 23, 2015
    #1
    I have a 5K iMac. I believe the thunderbolt speed is related or shared over one bus.

    I have an external Lacie Thunderbolt drive, as well as a OWC ThunderBay 4, four-bay drive enclosure with dual Thunderbolt 2 ports.

    If I connect the Lacie into the Thunderbay 2nd port, I lose 75 MB/s write speed, but keep the same read speed.

    My second Thunderbolt port I use for an secondary monitor using a mini display port to DVI adaptor.

    My question is, how much data transfer does a monitor use compared to an external Thunderbolt drive? If i connect the monitor into the 2nd thunderbolt port, how much of a performance hit will I get?
     
  2. loekf macrumors 6502

    loekf

    Joined:
    Mar 23, 2015
    Location:
    Nijmegen, The Netherlands
    #2
    4K display: 3840 x 2160 x 60 fps x 3 bytes-p-pixel = 1.4 GB/s (11 Gbps).. not taking protocol overhead (10/8 coding ??)
    into account, so let's say 60% if a TB2 connection. There should be plenty of room for an external drive.
     
  3. warrenl thread starter macrumors member

    warrenl

    Joined:
    Jun 23, 2015
    #3
    The monitor is Dell u2410, not a 4k monitor. I switched the Lacie from the back of the Thunderbay to the iMac 2nd TB port, and purchased a longer monitor cable (12') as the Thunderbay is as far away from my desk as I can get it on a 3m TB cable due to fan noise.

    On running tests after the monitor/lacie switch, I see better performance on the Laice TB external, and no loss of performance on the Thunderbay with the monitor attached. In fact I am getting improved read/writes of about 20MB/s without the Lacie attached, which is basically the same as the Thunderbay without any attached TB devices.
     
  4. matreya macrumors 65816

    matreya

    Joined:
    Nov 14, 2009
    #4
    I have a 5k iMac also, with a total of 8 Thunderbolt enabled drives on the two ports, and I've never noticed any speed drops. I have no Lacie drives though. 2 x Thunderbay IV, a G-Tech RAID array, a Lacie esata hub, a Mercury Elite Pro Dual & a Buffalo DriveStation on one branch, and 2 x Thunderbay 4 minis & an OWC Mercury On-The-Go-Pro thunderbolt connected SSD.

    I would suspect the Lacie TB External...
     
  5. warrenl thread starter macrumors member

    warrenl

    Joined:
    Jun 23, 2015
    #5
    Thanks for the feedback. Have you ever compared the speed of a single device on TB, compared to multiple at the same time?

    I get the same speed on my SSD if it is in the Thunderbay or the Lacie, but as mentioned not if the Lacie is connected to the Thunderbay.
     
  6. matreya macrumors 65816

    matreya

    Joined:
    Nov 14, 2009
    #6
    I've performed multiple file copies from a RAID0'd 4 x 500GB SSDs to my hard drives in both Thunderbays and not noticed any speed decreases... I monitor my disk traffic with a free open source tool called XRG

    http://www.gauchosoft.com/Products/XRG/

    I thought the Lacie was an external TB HDD - you swapped out the HDD to put in an SSD?
     
  7. warrenl thread starter macrumors member

    warrenl

    Joined:
    Jun 23, 2015
    #7
    Yes, I put a 500GB Crucial SSD in the Lacie TB enclosure
     

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