Very slow transfer speeds from one HDD to another

Discussion in 'Mac Pro' started by Xzag, Jan 19, 2013.

  1. Xzag macrumors member

    Mar 19, 2012
    Just established a RAID1 with two 3TB WD RED drives in the MAC Pro (2012 model). I am trying to copy a 1.65TB Aperture Library from a 2TB WD Black to the Red(s). Says 21 days, and I believe it as I check the progress (3.35GB in just over 2 hours.....My CF cards transfer faster!!!). What could be slowing this down? 110GB of music transferred pretty quickly just the other day in testing the RAID...Thanks in advance for any comments/suggestions.
  2. ashman70 macrumors 6502a

    Dec 20, 2010
    You don't mention how the RAID is configured, is this using a hardware RAID controller, or software RAID? The WD RED drives are 5400RPM drives, not particularly made for high performance, but NAS duty.
  3. Xzag thread starter macrumors member

    Mar 19, 2012
    software RAID 1, Mirrored set. The file finished overnight, which is good. It was REALLY slow at the beginning (,4GB in the first hour), then picked up speed. Total transfer was around 8 hours, but I was asleep, so could have been faster. Any ideas why the transfer would be bogged down in an Aperture Library?
  4. gnasher729 macrumors P6


    Nov 25, 2005
    Except on an SSD drive, large numbers of very small files tend to be transferred very slowly. Roughly speaking, transferring files might take 10 milliseconds per file plus 10 milliseconds per Megabyte. Tiny files will have a very slow speed in Megabyte per second. Unfortunately, that can put the time estimates off completely.

    Next time, open "Activity Monitor" and watch "Disk activity". You will find times with large numbers of reads and writes and very little data transferred, mixed with times of small numbers of reads and writes and huge amounts of data transferred.

    Another possibility is an actual defect on one of the drives. If bits of the drive surface are damaged, the drive can get stuck on one file for ages. In that case, Activity Monitor won't show any progress.
  5. Xzag thread starter macrumors member

    Mar 19, 2012
    thx gnasher. I had activity monitor open, and seemed to have data reads and writes in the Kb range, instead of Mb range. That is why I started to wonder. Black Magic was 80-120Mb/s on all the drives, depending on the test it was performing.

    The small file thing may make sense, because if Aperture Library starts from oldest to newest in the file structure, there are thousands of very small files when I was just a beginner. Then the large ones lately.

    What is the best way to check a disk? Can it have files on it while you perform the test, or do I need to format it?

    I will keep the library on the 2TB (plus a backup) for a few weeks to ensure that all is OK. Then I plan to revert the 2TB to a TM b/u of the system files on the 1TB Black that is the system drive. Would be nice to run the disk through it's paces before I made the switch.

Share This Page