USB Hard Drive set up as Time Machine - Unmounts randomly

Add me to the list; my particular problem is that when the computer goes to sleep, I wake it up and all of my external USB disks have been unmounted (with the error that they've been unmounted incorrectly) and my external keyboard and attached peripherals aren't recognized. The setup is:

13" MacBook (late 2008), Mac OS 10.5.6
One USB port has a powered Macally 7-port TriHub with these devices plugged into it:
External Keyboard (wireless USB and 1 external MyBook drive plugged into keyboard)
LaCie 500 GB BigDisk USB drive (for Aperture backups)
LaCie 500 GB USB drive (Time Machine)
Canon MX850 Multifunction Printer
(and sometimes a SanDisk SDHC card reader)

After sleep and failure to recognize any of these USB devices, I haven't found a way to get everything back - logging out and back in does not do it. Restarting does. I suppose I could try just disconnecting and reconnecting the hub, but that seemed a bit hinky, if there's any chance that I could damage the disks.

I'm starting to try and troubleshoot this by taking everything out and adding things back in, but it seems like there's no inherent reason why such a setup shouldn't work. It would be nice if I could use my external disks in their FW mode, but obviously that option is now gone with the MacBooks (and I knew that when I bought it).

(Note: I've tried remounting the disks via Disk Utility, but they are not seen at all.)

Message was edited by: sandrift

USB isn't the only interface experiencing this problem. My external hard drive connected via Firewire (WD MyBook) also unmounts randomly. But only when Time Machine is enabled and only since I updated to 10.5.6. Previously under 10.5.5 the problem didn't happen.

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USB isn't the only interface experiencing this problem. My external hard drive connected via Firewire (WD MyBook) also unmounts randomly. But only when Time Machine is enabled and only since I updated to 10.5.6. Previously under 10.5.5 the problem didn't happen.
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Me too! - using Firewire-800 to connect to an external Lacie drive. Only seems to have happened since updating OS-X to 10.5.6 - did not ever happen under 10.5.5 - do other users reporting this issue have OS at 10.5.6?

Same issue here. One WD 500gb connected to family iMac and a 500gb Simpletech connected to my MBP. Both USB, both self powered. Two Macs will sleep, but upon waking, the externals have been unmounted.

The MBP will give me the "device removal" error and pick up where it left off with regards to the Simpletech. Curiously, the iMac will simply just not see the WD drive any further until I remove the USB connection and reconnect. At that moment Finder/Time Machine discovers the drive once again- but then begins a full back up. This occurs every morning after I wake up myself and put the iMac through its paces first thing. This is just a tad annoying to do this every morning, whereas the MBP simply gives me the error and life goes on as normal.

Neither of these occurrences were normal operating procedure when the drives were first purchased and used as Time Machine drives. I was thinking that the iMac's TM might possibly be corrupt? But perhaps it is the update that everyone is referencing.

I did confirm with Apple that 10.5.6 did introduce mounting errors with Time Machine. But specifically with WD Studio II drives I determined that the WD Drive Manager software was causing my problems. WD had never heard of it, but I have not had the problem reoccur once that software was uninstalled.

I also get the same problem on my brand new MacBook Pro 2.4 ghz (late 2008) with a iomega external hard drive. I was using the same drive with my PowerBook g4 12" 1.5 ghz without a problem (plugged with firewire on the powerbook) Since i don't have a fw 800 adapter yet i haven't been able to test this drive plugged with firewire instead of usb on my MacBook Pro.

I just installed a brand new hard drive into an external firewire case and after partitioning the drive and making it a time machine drive it unmounts randomly. I cant even start a time machine backup because anywhere between 5 and 10 seconds later the drive unmounts and TM errors out.

I didn't see any solutions posted in this thread. Has this problem been addressed anywhere else?

Hello All

Had the same problem. Started with random dismounts. The drive in question is a LaCie 1TB big disk extreme+.
I tried switching connection from FW to USB. Worked for a while. Then I tried the drive with another computer and it mounted. I checked all my ports, USB and FW, with other devices, no problem.
Finally the drive wouldn't mount anywhere anytime.
Here is a quote from LaCie support — "A faulty power supply may not be supplying enough power to fully spin up the drive. This can cause all sorts of erratic behaviour. Please try the drive with a different power adapter from another LaCie drive (must be a LaCie adaptor with the same power specifications, an adaptor from a different drive manufacturer can damage the drive and void the warranty)."
This solved my problem. This process took about a month during which time I thought maybe the drive was fried, maybe my computer was fried, maybe my desk is in a magnetic anomaly.
I think " This can cause all sorts of erratic behaviour " covers a lot of the problems seen in this and related threads. If you can try another power converter, it's certainly worth a try.

Hi Terry,

I finally chased down my issue. It turns out something is wrong with the front firewire port on the mac. It's intermittent. It functions for a few minutes then doesn't. Moving the drive to the rear connector solved the issue. I cant say why that front port is bad. I never used it previous to this.

Eric

Hi,

I received my firewire 800 cable this week and my hard drive hasn't unmounted unexpetedly since then. Maybe it has something to do with USB??

I reckon its the Sleep Feature in Energy settings. I was about to use my iomega 250GB USB drive as a frisbee but thought i better check here first.

Drive always dismounts randomly. But now that I've disabled 'Put to sleep' setting, its fine (hasn't dismounted for the 10 minutes since disabling).

I also have a Seagate FireWire drive and have NEVER had any probs with it.

I've tried much of what has been suggested - none of it helps. I can't help but think it had something to do with a recent OS update. No one has found a definitive answer?

The same here. a WD 500 GB via USB unmounts and remounts randomly on Tiger 10.4.11 since a few weeks, strange!

Did Apple say anything about fixes or just confirm that there was a problem? I have a Fantom GreenDrive 1TB, but all the software on it was wiped when I formatted it, so I don't think that could be causing the problem. It was fine for a while, then it started occasionally randomly unmounting, which was annoying but not problematic, but starting today I can't even complete a full time machine backup without it unmounting.

Problem supposedly solved with updated Seagate drivers...

See discussion:

http://forums.seagate.com/stx/board/message?board.id=freeagent&thread.id=3723&vi ew=bydateascending&page=2

Drivers are here:
http://www.seagate.com/www/en-us/support/downloads/freeagent/seagate-diag-mac