Target disk mode thunderbolt speed slow?

Discussion in 'OS X Yosemite (10.10)' started by erastfandorin, Mar 5, 2015.

  1. erastfandorin macrumors newbie

    Joined:
    Mar 5, 2015
    #1
    I have a mid 2013 Macbook Air with blazing fast 256gb ssd and a 2011 Mac Mini Server with a 512gb crucial mx100 ssd and a 2tb m9t hdd.
    Both running Yosemite 10.10

    Using Blackmagic Disk Speed Test the Macbook Air hits around 680MB/s write and 700MB/s read. The Mac mini ssd hits around 480MB/s write and 500MB/s read.

    I connect them via Thunderbolt and restart the mini in target disk mode.
    When sending files from the Air to the mini ssd the speeds average around only 150MB/s.
    Is this normal? What sort of speeds are other users getting in similar ssd to ssd transfers?
    I've tried varies sizes and types of files with similar speeds.

    I had really expected the transfer speeds to be approaching 300MB/s. Am I right in thinking thats the sort of speeds that should be possible?
    Whats causing the slow down? is this really as fast as target disk mode gets?
     
  2. stempsons macrumors regular

    Joined:
    Feb 15, 2014
    #2
    what's are the speeds when selecting the mac mini target disk from the macbook air's black magic app?
     
  3. erastfandorin thread starter macrumors newbie

    Joined:
    Mar 5, 2015
    #3
    I've not actually tried that yet... Ill do it right now. :)

    ----------

    Doing as you said on the mac mini ssd write speed is around 135 and and read is around 185!

    Why is this? Its pretty disappointing!

    As I said the Crucial ssd hits around 500MB/s when testing from the mac mini.

    Thanks
     
  4. stempsons macrumors regular

    Joined:
    Feb 15, 2014
    #4
    Hmm, that's very strange. I'm getting almost native speeds through thunderbolt with a similar setup. I'm using a 2014 mac mini with fusion drive as a file server to my mac pro, and speeds are over 400+ write, 600+ read...Not sure what the issue is with your setup :(
     
  5. erastfandorin thread starter macrumors newbie

    Joined:
    Mar 5, 2015
    #5
    Yeah its really strange... No idea whats causing it. Are you running your mac mini in target disk mode then yeah?

    Anyone else notice slow speeds via thunderbolt?
     
  6. stempsons macrumors regular

    Joined:
    Feb 15, 2014
    #6
    No, I'm just running it without a monitor and using a shared folder for iTunes and photo storage. I've tested it both ways, and transfer rate is the same through thunderbolt.
     
  7. erastfandorin thread starter macrumors newbie

    Joined:
    Mar 5, 2015
    #7
    Just tried something else there with strange results...

    I had been setting the mac mini in target disk mode when transferring files but instead this time I put the macbook air into target disk mode.

    This time file transfers were what one would expect! Over 300MB/s.
    That baffles me even more. Why would it matter which computer is put into target disk mode?

    In the future I'll simply put the macbook in target disk mode instead and that solves the problem.

    But can any technical folk tell me whats behind this??

    Thanks
     
  8. erastfandorin thread starter macrumors newbie

    Joined:
    Mar 5, 2015
  9. rockdirector macrumors newbie

    Joined:
    Aug 31, 2012
    #9
    As I understand it, Target Disk Mode run on EFI and doesn't have the full TB functionality of the OS.
     
  10. mr_bam macrumors newbie

    mr_bam

    Joined:
    Jun 23, 2003
    Location:
    Wales, UK
    #10
    I'm having this same problem with a Mid 2015 MacBook Pro 15 inch who's SSD scores 1800MB/s read and write using File Vault and 10.13.1. Over Thunderbolt 2 to Thunderbolt 3 (via Apple's dongle) to a 2017 MacBook Pro 15 inch who's SSD also scores 1800MB/s read/write. The transfer from the old one is only 150MB/s at most when the 2015 one is in Target Disk Mode.

    I'm wondering if in TDM FileVault doesn't have hardware decryption perhaps? It's rubbish. The USB3 Spinning 2.5 inch backup clone I have isn't that much slower than direct transfer... but it's hours to transfer 500 to 750GB!! So annoying. Advanced tech?!

    I've done TDM transfers before (year or two ago) on two MacBook Air's (2011 to 2013) and they were lightening fast.

    Why am I upgrading? Forced to because the MBP2015 seems to lock up when the GPU heats up. I haven't figured out the exact cause yet but I have loads of work to do so I've just had to get the new one and will deal with the old one later.
     

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