External USB Hard Drive suddenly got really slow!!!

Discussion in 'Mac Accessories' started by mikearce, Apr 26, 2012.

  1. mikearce macrumors newbie

    Apr 19, 2012
    Ive had a Western Digital My Book USB 2TB External Hard Drive for a while. Never gave me any problems.

    Today I noticed while streaming video content from it that the stream itself was slower than usual. I went to my imac opened it in finder and it takes forever to even display the folders. I opened one of the folders where I had a bunch of videos and it just keeps reading but wont display them, just keeps reading. Transfer speeds are REALLY slow too.

    I went to Disk Utility and verified it and it says everything is OK. I even booted the imac from the Lion Recovery Disk and tried it again. Same thing. Says everything is perfect! I ejected it and plugged it into my MacBook Pro and same thing. Extremely slow both while reading and writing or transfering files.

    I have other WD usb external hard drives and they all work fine. Im starting to lose it cuz I have a lot of important stuff in there.

    Any help would be really appreciated!

    iMac specs:

    27-inch, Mid 2011
    Processor 3.4 GHz Intel Core i7
    Memory 16 GB 1333 MHz DDR3
    Graphics AMD Radeon HD 6970M 2048 MB
    Software Mac OS X Lion 10.7.3
  2. murphychris macrumors 6502a

    Mar 19, 2012
    Try a different cable and also get anything important off of it as soon as you can.

    "Verify" only checks the directory structure. That can be fine as long as the disk is successfully performing error detection and correction and what you're describing is a disk that's getting a lot of read errors, but is correcting them. So the file system says "I'm fine" even though the disk is having issues.

    When you click on the disk icon in Disk Utility, at the bottom what does it says for SMART Status?
  3. simsaladimbamba

    Nov 28, 2010
    You can use the following applications to benchmark the speed of your HDD to see, if it is that slow:

    Also make a backup of that data, if it is that important.

    Here is how I backup my important data:
  4. chrisg02176 macrumors newbie

    May 31, 2013
  5. mwhities macrumors 6502a

    Jul 13, 2011
    I did a lot of data (400Gs+) moving last night and I noticed a big slow down accessing it after. I also installed Lion installer on it to instal Lion on my Raid0 320s and it took 15 minutes for the install screen to come up. It kept stopping saying to try reinstalling.

    I googled that and it said to reset PRAM. After I did that, it installed properly and seemed to transfer faster. Maybe that that and report back.
  6. brand macrumors 601


    Oct 3, 2006
    You could pull the drive from the enclosure and run SpinRite on it.
  7. murphychris macrumors 6502a

    Mar 19, 2012
    I'd sooner suspect mds or mdworker (spotlight processes) were involved in updating the index on that disk, which slows things down immensely. Or a backupd process from/to this disk which also slows things down immensely. So I'd go to Terminal and run the top command. Or look at Activity Monitor with the top pop-up menu set to All Processes, then click on %CPU column so it sorts by most to least CPU usage. See what process is hogging the most processes, and if it's possible that process is using the affected drive.

    Another possibility is that the disk has developed marginally bad sectors. This will cause long delays as the drive firmware ECC corrects for the problem. So long as the read is eventually successful, an error usually isn't logged. But you could run 'sudo dmesg' from Terminal and search through that pile of complexity for something related to the /dev/diskX device in question. If you don't know what X is for your disk, then use 'diskutil list' for a listing.

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