external drive gone awol

September 2, 2011 12:36 PM

I have a 2TB Western Digital "My Book Essentials" external drive for Time Machine that has gone missing. Its icon sat on the desktop till sometime in the last day or two, and now Snow Leopard and Disk Utility can't find it anywhere. I have rebooted, unplugged/replugged, changed USB ports, changed outlets for its power adapter, etc. It is still running as usual, nice and quiet with its tiny light on. It still powers up when plugged in. No weird sounds. I plugged it into a Windows computer and it was recognized as an unreadable USB device (since it is formatted for Mac). So apparently it is still a functional something. My secondary TimeMachine drive, also a WD My Book, is still recognized and running as usual. Any help or ideas? Thanks!
posted by methinks to computers & internet (19 answers total)

Sounds like it just isn't mounting properly.
First thing you want to run is an fdisk, to see what you can see.
Better yet, try following these directions. I don't know how far command line mac is from command line linux these days, but you should be able to make it work with some tweaking.

..or wait for some helpful mac user to come correct me.
posted by Stagger Lee at 12:44 PM on September 2, 2011

Format aside, unreadable might mean unusable. Can you use any utilities in Windows to see if the system can determine the make/model of the drive? If it shows up as a USB device only, and you have no option to format the drive for Windows use, odds are the drive is dead, and Windows is only recognizing the USB interface you just plugged in.

Don't lose hope though. A colleague of mine had his external WD drive die. I dissected the case, and found that the drive inside was perfectly fine, but the electrical components running the interface between drive and computer was apparently broken in some way. If the drive is OK, OWC Computing sells some pretty cheap, reliable USB/FireWire drive cases. If the drive is hosed, you might still have an easier route to upgrade by buying drive and case separately (I have a 2 TB WD drive in a case from OWC for TimeMachine, cost me about $80 when I bought the parts)
posted by caution live frogs at 1:02 PM on September 2, 2011

HFSExplorer is a Java app that runs on Windows that can mount Mac drives. It's handy to have around. Otherwise, what caution live frogs said.
posted by infinitewindow at 1:04 PM on September 2, 2011 [1 favorite]

Thank for this all, thus far. HFSExplorer doesn't see anything in Windows either, and Device Manager only sees an "unknown device".
posted by methinks at 1:25 PM on September 2, 2011

Do you have / have you tried TechTool? It's allowed me to mount otherwise unmountable disks, which I've then cloned to new drives.
posted by Admiral Haddock at 2:00 PM on September 2, 2011

I would suspect a failure in the SATA-to-USB circuitry in the WD drive. It's happened to me before, with WD MyBooks. Open it, get the drive out, and try it in another enclosure.
posted by krilli at 2:05 PM on September 2, 2011

Vantec makes nice USB/ESATA enclosures.
posted by flabdablet at 4:28 PM on September 2, 2011

I've had a similar problem in 10.7, but I imagine this may work in 10.6 just as well.

First, see if Disk Utility is capable of verifying/repairing the disk. You may want to close all other applications before doing this, as otherwise it is likely that your computer will hang for a while.

If that doesn't work after about 30 minutes, from the terminal call something like
    sudo killall diskutil
    sudo diskutil unmount /dev/_devicename_
    sudo fsck_hfs -fd /dev/_volumename_
where _devicename_ is the handle for the disk containing the volume and _volumename_ is the handle for the volume that won't mount (along the lines of disk1 and disk1s1, respectively; if you're unsure, unmount all external drives and choose the one that isn't present when you call mount with no arguments). These commands will, in order, stop Disk Utility's attempt to repair the disk, ensure that all volumes associated with the disk are unmounted, and repair the filesystem on the volume that is giving you trouble. You may need to call the last command multiple times, until it no longer returns any errors.

The longer that you use a physically damaged disk, the higher the probability of damage. If you think that the problem is in hardware, replace it ASAP once you've recovered your data. Otherwise, it's entirely possible that Mac OS X simply failed to unmount the disk cleanly. The problems I've seen seem like they're associated with the directory hard linking used to implement Time Machine, so make of it what you will. Perhaps someone here is better informed on the matter.
posted by pmugowsky at 5:37 PM on September 2, 2011

Thanks, pmugowsky. Disk Utility (the whole computer, actually) doesn't even seem to see the drive in question.

If I try to place this drive into a new enclosure, does it matter if the new housing is USB 2 or 3 (it is built inside a USB 3 box)?
posted by methinks at 5:45 PM on September 2, 2011

Hmm. So it doesn't show up at all under /dev? Sorry for the poor reading comprehension, in any case.
posted by pmugowsky at 5:53 PM on September 2, 2011

First, shutdown (rather than restart) the computer. Perhaps your USB ports are messed up somehow. A shutdown resets them by removing power.

Second, open Terminal and type
diskutil list

If the drive doesn't show up there, it's probably a hardware problem rather than disk format corruption. As suggested by pmugowsky and krilli consider a new enclosure.

TechTool and DiskWarrior can help repair a disk if it can mount, but if it isn't seen on the USB bus, there isn't much you can do.

I would first shutdown the computer entirely, remove the cable connecting the drive, reconnect everything, and power up. That sometimes help with crazy situations like this. Good luck.
posted by blob at 7:44 PM on September 2, 2011

Thanks, blob. I followed your method and terminal did not find this drive, which I guess might be good news if I can simply rehouse this and resume use.
posted by methinks at 8:35 PM on September 2, 2011

I've had so many failures with MyBook external drives that I will no longer buy them. It's always the enclosure, not the drive, so odds are you can save the data. Look for a SATA dock -- it's an easy way to mount and test drives.
posted by mmoncur at 2:59 PM on September 3, 2011

That's good to know, thanks. I'll report back once I've had a chance to try this outside its enclosure.
posted by methinks at 8:54 AM on September 4, 2011

A SATA dock is indeed a useful gadget to own if you're in the habit of testing lots of SATA drives. But if what you actually want is something that replaces the form and function of your present MyBook, you'll want a standard drive enclosure. Aluminium cases are better than plastic, and ESATA plus USB is better than USB alone.

If you're ordering an enclosure online, get two. This will save you shipping costs when (not if) the rubbish USB interface board in your second MyBook craps out.
posted by flabdablet at 9:03 PM on September 4, 2011

Well, I installed this in a nice Rosewill case and get the error message "The disk you inserted was not readable by this computer." with the options to Initialize, Ignore or Eject.

System Profile sees the 2TB USB2.0 storage device, with an unknown Partition Map Type and its SMART status unknown.

Disk Utility also sees an external 2TB Western Digital read/write device as Unformatted and its SMART status Not Supported.

I'm assuming all of this means the drive is still usable.

Do I need to rename this drive somehow to its original name?

Could there be a problem with this new USB 2 enclosure, since it was originally in a USB 3 case?

Do I need to try Disk Warrior to repair something?
posted by methinks at 10:49 AM on September 8, 2011

I forgot to mention, Disk Utility does not give me the option to do anything to verify or repair this drive, it only recognizes that the device and volume exist in the correct location.

My objective is to restore the thing so its contents are not lost. At the least, I like to reformat so it can still be used.
posted by methinks at 11:03 AM on September 8, 2011

The fact that the drive size is recognized is hopeful. SMART not being available doesn't mean much (lots of USB interfaces don't pass the SMART command set through properly, which is why I recommend ESATA-capable enclosures for this kind of work).

There are two possibilities here, as I see it. First is that your WD USB interface failed in such a way as to write rubbish to the partition table (hope!); second is that the drive itself really is unreadable though its onboard controller is still working well enough to report its size (o noes).

You should be able to distinguish between these two cases by attempting to copy raw blocks from the drive to /dev/null using dd. If that succeeds, you'll want to buy a second drive the same size, use dd or Gnu ddrescue to image the first drive onto the second drive so you have a backup for when (not if!) things go wrong, then run some kind of partition table rebuilding and file recovery tool against the copy. I'm sure somebody with more Mac experience than I have can recommend suitable tools.
posted by flabdablet at 4:45 PM on September 8, 2011

This is great help, flabdablet. Thank you.

I wondered if it could have anything to do with incompatibility with this new enclosure, though I'm admittedly grasping at straws.

I did make the relatively expensive experiment of buying DiskWarrior, sat for a couple of hours while it read the disc, and received the error message that "Directory cannot be rebuilt, the size of this Standard Disk cannot be supported"; a) the disc appears to be a Mac OS Standard disk, b) the disk does not appear on the desktop, and c) is too big (at 2TB) for it to be able to work with. So that's that, for now.

These instructionals look coherent for a Utilities novice like me, so I'll see if I can make anything of them.
posted by methinks at 5:49 PM on September 8, 2011