external firewire hard drive slows down from 80mbs to 40mbs speed almost randomly

Discussion in 'Mac Accessories' started by Jottle, Jun 15, 2010.

  1. Jottle macrumors 6502

    Joined:
    Oct 17, 2003
    #1
    This is the strangest hardware problem I've come across. I'm running a unibody mbp (June 2009) with an external WD 2.0TB Caviar Green drive mounted in a firewire 800 enclosure made by icydock.

    Lately, I've noticed that after an unknown amount of uptime, the speed of file transfers to the WD external drive slows down dramatically. I figured this out by watching my time machine transfers take a bit longer after awhile, and I verified this using aja system test and speedutilities.

    When I boot my mbp in the morning, file transfers and time machine backups to the external WD transfer at a rate of about 67-75MB/s. This is the speed the drive should always be working at since it's connected via firewire 800. Aja speedtest verifies the speed is as it should be as well.

    Then, after a couple hours of using my mbp, or even later in the day, I'll transfer a file to the external WD or run a time machine backup and find that the transfer will only run at a max of 29-35MB/s. This is exactly half the speed the transfer should be going at. Subsequent transfers stay at this slower rate no matter what I do.

    However, I've been able to fix this problem by unmounting and remounting the external WD or restarting my mbp. After doing either of these actions, the WD external goes back to contant transfers at 75-80Mbs. So something is happening where the longer the mbp is running, or after some sort of disk activity, the external WD reverts to a slower transfer speed (closer to FW400). I can't isolate whether it's an issue on the mac os side or the hard drive or the hard drive enclosure because I can make the hard drive go back to optimal speed again merely by unmounting and remounting it. This works consistently until a few hours later when the drive begins to handle transfers at half speed again.

    I run hourly time machine backups to the drive. The time machine backups can't be the culprit because the drive remains running at optimal speed after the backups (verified with aja system test and speed utilities)

    Any possible ideas as to why the drive cuts down to half its optimal transfer rate after a bit of time? I can't figure out the cause of this, and the consistency of the drop leads me to think this is an issue with the power management on the drive since it reverts to full fw800 speed when I umount and remount the drive or restart my computer. Could this be an OSX issue where for some reason the system isn't negotiating the fastest speed?

    Any help appreciated.
     
  2. frankowen macrumors newbie

    Joined:
    Aug 1, 2007
    #2
    I am having EXACTLY the same symptom, but on a 24" iMac. In my case, I have a Seagate FreeAgent 1.5TB external drive, and when it is at "full" speed, I see transfer rates in the 40-60MB/s range. When it slows down, it is exactly half this, or 20-30MB/s. Unmounting and remounting always brings it back to full speed again. In some case, I found that putting the Mac to sleep and then re-waking can help too..

    Sorry I don't have a solution, but at least you know it's not "just you". It is really annoying to have paid for FW800, and only getting FW400 speeds.
     
  3. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #3
    I don't see any mention of cabling here; have you (or the OP) tried another FW800 cable? I could imagine that if there's something wrong with the cable the drive might fall back to FW400 when it crosses some threshold of errors.

    I admit to not having any idea whether a FW connection will do this, but trying another cable is always worth a shot when you've got an intermittent problem like that.

    Recently solved a network issue doing exactly that when it turned out a pre-made cable that had been just fine previously went bad. I could have spent hours fiddling with things if I hadn't tried the cable. (For what it's worth, my NewerTech FW800 case seems to have no problem maintaining full FW800 speeds over time and through sleeps, although it will occasionally connect mistakenly to the USB2 port instead of the FW one on a cold boot.)
     
  4. Jottle thread starter macrumors 6502

    Joined:
    Oct 17, 2003
    #4
    Glad to hear I'm not the only one with this strange issue. I do have other cables that I've tried, but not for an extended period of time. I think that's a good next troubleshooting step. If it does it on a different cable, I don't know what I'll do to solve this. Lately, I've been preventing the disk from spinning down at all. However, this hasn't solved the problem for me. I hope someone else will chime in soon who has found a solution to this issue.

    To me this sounds like an OSX issue, but I can't be sure.
     
  5. Jottle thread starter macrumors 6502

    Joined:
    Oct 17, 2003
    #5
    I still doubt this is a cable issue. What I've done is set the hard disks to never spin down (via system preferences). I leave my computer on for weeks, only sleeping it at night and waking it up in the morning. So far, I haven't had any slowdowns since I implemented these features. This may be a communication issue with mac osx's spindown command and my WD green drive or the external case that it's mounted in. Hard to tell at this point. However, not spinning down the drive, except for when the computer goes to sleep, has solved the issue for me. I'd still like to be able to spin down the drive as it saves energy. I'll report back if I can figure anything else out.
     
  6. Jottle thread starter macrumors 6502

    Joined:
    Oct 17, 2003
    #6
    No updates yet. I still haven't figured out why this happens.
     
  7. POX macrumors member

    POX

    Joined:
    Jan 15, 2009
    Location:
    Oporto, Portugal
    #7
    I have the same problem with a Onnto AT-S111 2.5" FW 800 connected to uMBP late 2008.

    My normal transfers speed are around 55MB/sec but sometimes drop to 30MB/sec.

    The solution is unmount and re-mount the drive.
     
  8. Consultant macrumors G5

    Consultant

    Joined:
    Jun 27, 2007
    #8
    Disk read / write speed depends on many things.

    Whether it's reading / writing
    how big the files are
    whether they are sequential or random
    etc.
     
  9. POX macrumors member

    POX

    Joined:
    Jan 15, 2009
    Location:
    Oporto, Portugal
    #9
    The file for testing is a 700MB divx movie.

    Before re-mounting write speed is around 30MB/s and after 55MB/s.
     
  10. Jottle thread starter macrumors 6502

    Joined:
    Oct 17, 2003
    #10
    Glad to see I'm not alone with this issue. But not happy that we're all still experience problems with it. The only way to fix it for me has been to do the exact same thing as you: remount the drive after unmounting it. I think this is an osx issue and not a drive issue really. I think my carbon copy clone backups to this drive may be affecting it in some way, perhaps changing some temp settings for throughput. POX, do you use a cloning software like carbon copy cloner or superduper?
     
  11. POX macrumors member

    POX

    Joined:
    Jan 15, 2009
    Location:
    Oporto, Portugal
    #11
    No, I don´t use any cloning software.
     
  12. Jottle thread starter macrumors 6502

    Joined:
    Oct 17, 2003
    #12
    Hmm. It could be some sort of incompatibility between the hardware in the external hd enclosure and the mac. My issue is with a WD20EARS (2TB) drive enclosed in an icydock MB559UEB-1SB enclosure connected via firewire 800 cable. What is everyone else using that has this problem?
     
  13. POX macrumors member

    POX

    Joined:
    Jan 15, 2009
    Location:
    Oporto, Portugal
    #13
    My enclosure is a Onnto AT-S111 with a HD seagate momentus 500GB 7200.4.
     

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