USB Hard Drive set up as Time Machine - Unmounts randomly

Yvan,

It may be that the drive has a sleep feature that kicks in after a period of time. The manufacturers website might have more details on this. Nevertheless, there might still be something that you can do:

Go to System Preferences --> Energy Saver.
Click the "Sleep" tab.
If there is a check mark beside "Put the hard disk(s) to sleep when possible", uncheck it and see if that makes a difference.

Let us now if this is helpful.

Cheers!

Yvan,

To what is the drive in question attached? If to your Mac, then this behavior is puzzling, because TM should be automatically ejecting a drive directly attached to the Mac.

If however, the drive is attached to the USB port of an Airport wireless device (you never specified this), then "Yes", Time Machine will eject the drive automatically as it is regarded as Network Attached Storage (NAS). For the sake of network stability and bandwidth, TM always ejects NAS drives once a backup is complete.

Glenn

I have been having excatly the same problem recently.

I have a 500gig USB 2 external drive hooked up to my Mac via a USB hub (NOT airport at all) for Time Machine, I also have 2 other external drives hooked up through the same hub.

Just recently (about a mouth ago?) the time machine drive randomly and frequently unmounts. I get that lovely little 'device removed' error message, and then the drive mounts again.

Time Machine seems to still be working (thankfully), but this is getting very annoying and is defiantly a new behaviour.

Any suggestions on what to try would be appreciated.

I have the same problem, but it is happening with various USB drives including an iphone. If I have any of these connected via a USB hub to the MacBook Pro, they mount and operate fine until I attempt to copy large files to them. Randomly, during large file transfer, the drive will suddenly disappear and I'll get the same error as if I had yanked out the USB cable without unmounting it.

This is happening with:
* A standard (Lacie) powered 500GB USB drive mounted normally.
* A standard (Lacie) powered 500GB USB drive being used as a Time Machine disk (it errors/unmounts during Time Machine backups).
* An iphone 8GB during itunes syncs, only when copying large files (like videos).

I have tried two USB hubs, one powered and one not, and both cause the same problems. If I connect any of these drives/iphone directly to the Mac then they work absolutely fine.

I first thought the (unpowered) USB hub was to blame, but when I started using the powered USB hub and saw the same problems I'm starting to wonder if OS X has a bug with regards to heavy I/O to USB devices connected through hubs...?

Davros: my tip would be to connect the drive directly to the computer (not via USB hub) and see if the problem goes away.

Yvan Zivkovic wrote:
Hey everyone,

I recently purchased a Seagate FreeAgent USB 2.0 External Hard Drive which holds 1TB. I plan to use it to backup what's on both my internal 80GB and my external 500GB.

However, lately, throughout the day, the drive seems to unmount itself for no apparent reason. I'm not aware of any log to check this (and if there is one, someone please let me know). Nothing appears to be wrong with the drive itself, it just seems to unmount randomly, it even unmounted whilst I was typing this.

I've tried switching USB ports, turning the device off and back on, and looking up the problem further, but I cannot find out why this is happening.

Can anyone enlighten me?

Is the drive powered from the computer USB port or does it have its own power?
I personally do not like using USB for external drives. The tend to drop to USB 1.1 on occasion and sometimes shut down on their own. My HDTV Stick only works in one of my MBP ports. In the other it works for about an hour and then drops off. It is powered by the computer.

Okay, I tried connecting the drive directly to the computer, and the problem still happens. Its still only the Time Machine volume that is affected.

My drive is self powered (pluged into the mains), and my hub is usb 2 and is powered too.

I'm having the exact same problem with an external iomega 500GB USB II drive attached directly to a new MBP. As long as Time Machine is on, the external drive frequently unmounts. With Time Machine off, it stays connected fine. Prior to when the unmounts started happening a few days ago, I got a message that the backup disk was full and Time Machine was throwing away backups to make room. I don't know if the problems started after that or after a Software Update that I accepted, but it had been running smoothly with Time Machine for the first ten days or so after first using it with this laptop.

I have also turned off disk spin-down on energy savings to no avail.

Thanks for any ideas,

Dave

Correction... I've stopped TM and left the external USB drive mounted on the desktop. It randomly disconnects without TM running.

I have the same problem. I use either a 4GB usb drive or a Western Digital 160 GB external powered hard drive. It has happened with my computer at home (14in. ibook G4) and with the computers at school (they're newer imacs with the new OS). It seemed to have started after I downloaded the most recent update that was supposed to improve USB functionality.
The other problem that I see it when I try to eject the usb drive, the computer hangs for a while, then says that it could not eject... quit any running programs and try again. Well, it sure does the same thing, so I now just yank out the usb drive instead of trying to eject it. Although, on my friend's ibook one time it did eject after telling it to eject.

I think it has something to do with the update from Apple.

Got the same annoying issue here with MBpro an external 2.5" USB 2.0 disk that randomly under heavy IO unmounts 😟 Also believe this might be due to some resently update from Apple

Hi I just noticed the same thing happen. Could be coincidental but it started after a software update to Mac OS X 10.5.6. The strange thing is that the USB hard drive has been working well as a Time Machine back up until after the software update.