1. iMore Question's Avatar
    I'm trying to find out if anyone else out there has this problem (or am I just lucky?)

    I have a WD MyBook that's about 3 years old. When using Yosemite it seems to like to show up as an attached drive whenever it wants to, or maybe I should say whenever Yosemite will allow it to - that's the question.

    I thought this was a hardware problem like the drive or the cable being bad. I used Scannerz on it to evaluate the external HDD, cable, and system. When the drive shows up after booting I was able to test the following with Scannerz:

    1. The external HD - no problems
    2. The cable - no problems
    3. I/O subsystem - no problems
    4. CPU and memory - no problems

    It found no problems with anything. SMART checks on the drive show no problem. NOTHING is showing any problems.

    This is a strange problem, almost like at boot time the OS is deciding whether or not to allow the drive to connect, and after making its decision the drive will either show up or not. If it shows up, it's perfectly accessible, if it doesn't show show up, it's like the drive isn't even connected. It's almost like it's being rejected for some security conflict.

    Here are some more details about the drive:

    1. It's USB
    2. It's a WD 2TB MyBook for Mac
    3. Drivers are NOT installed
    4. Swapping out cables didn't help either
    5. It's passed every possible test I can throw at it using Scannerz, smartmontools smartctl, etc..when it's seen
    6. It's a regular HFS formatted drive.
    7. It's a direct connection, no hubs in the way
    8. It works fine with an old iMac I have running Snow Leopard

    Is this a Yosemite bug? Is anyone else having problems like this.

    05-04-2015 01:39 PM
  2. kch50428's Avatar
    I've not seen this with my MyBook on my MacBook Pro...
    05-04-2015 01:42 PM
  3. Mr-iMac's Avatar
    I'm beginning to wonder if this isn't a security problem. A long time ago I installed the WD drivers, but when people started complaining about them causing data loss, I removed them, or at least thought I did.

    I understand that on third party SSDs TRIM isn't supported and third party TRIM enablers apparently can't be installed.

    I'm sort of thinking that maybe there's some remnant from the WD drivers in the system somewhere that I didn't get out, and now, depending on the state of the drive at boot, it either does or doesn't load it. When it fails it blocks it.

    Maybe that doesn't make 100% sense, but neither does this problem.
    05-04-2015 04:49 PM
  4. eugenb10's Avatar
    Scannerz is a pretty thorough tool, so I think you can rule out hardware problems. I think you can also rule them out because you said the drive works on an old iMac, so that pretty much totally rules out the drive itself.

    Some people have some problems with particular drives on particular systems running particular variants of OS X. Most, however, seem to have to do with the drive being ejected after waking up from sleep. Your problem is more peculiar than that.

    Here are some things you can try:

    1. Put a USB hub in between the drive and the system. Some minor incompatibilities can apparently exist between the firmware of the drive and the system, and in some cases this trick basically masks them.

    2. Update the drive's firmware

    3. Check WD's site to see if others are having the problem.

    4. If possible, put a clean install of Yosemite on a different drive or partition (totally clean!) and see if the problem exists when that's booted.

    5. See if the problem exists when booting in safe mode.

    Personally I'm guessing you might have done an update install and there was something leftover from the previous install that's creating compatibility problems. If you're familiar with the Unix command line tools, you may want to navigate to /var/log and look the log files to find what happens after the booting process starts and see if it identifies something going wrong.
    05-05-2015 03:25 AM
  5. Mr-iMac's Avatar
    I switched to 10.10.4 and the problems went away. I'm in the beta program. I have no idea what the other problem was.
    06-03-2015 01:58 PM
  6. Mr-iMac's Avatar
    It's been a few months and a few versions ago since I posted the original comment. The problem definitely was with Yosemite 10.10.3. It went away with 10.10.4 and I'm using both 10.10.5 and beta Yosemite as well and it hasn't surfaced again. I just thought I'd put this out there for confirmation if anyone else is having that problem and they're using 10.10.3.
    kch50428 likes this.
    08-25-2015 01:21 PM

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