External USB disk causing OS X shutdown to hang

Question

I'm looking at an iMac running OS X 10.5.8 and it has an annoying problem.

It has an external USB disk for Time Machine and it will normally shutdown okay.

However if the machine has been asleep and then woken up and then a shutdown attempted it seems that the USB disk won't respond to a request to eject and therefore shutdown hangs (powering the disk off will release the shutdown)

Any thoughts on why this might be, and where to start fixing it most welcome.

The obvious, but tedious fix is to eject the disk manually prior to shutdown, but I'm looking for automatic.

Answer 1

It's possible this is also caused by a corrupt metadata index having problems being rebuilt. Powering off the disk to finish the shutdown will just exacerbate the issue. Next time you have a problem ejecting it, I'd suggest running an 'lsof +D /Volumes/DriveName' in Terminal and see if 'mds' has it open. If so, you may want to rebuild the indexes from scratch (which can take a while, fair warning). Run 'mdutil -as' and take note of the indexes on that disk. If it's a Time Machine volume there will be a index for both the disk and the Time Machine 'backups.backupdb' directory. For each index on that disk, run 'mdutil -E /Path/Displayed/By/Mdutil-as'. mds will then rebuild the indexes. This can take a while. In the future, anytime the USB drive is unexpected disconnected, you may need to redo this.

Answer 2

• in Disk Utility, try running a Repair Disk on the entire drive.
• Is your external drive from Western Digital? Many of them have a built-in behaviour of spinning down after 10 minutes of inactivity. This may or may not be overridden by unchecking "Put the hard disk(s) to sleep when possible" in System Preferences > Energy Saver, but don't bet on it. (If that's the case for you, though, this may be a helpful workaround, or you could automatically run a command via the logout hook.)
• If you started using your drive as it was out of the box, it may still be formatted with FAT32. If you do try erasing the disk: using Disk Utility, select the entire disk, click Partition, select 1 Partition under Volume Scheme, format as Mac OS Extended (Journaled), and be sure to click Options... and select GUID Partition Table (or Apple Partition Map if your CPU is a G5 or earlier). This will do a more complete format than a simple erase.

Answer 3

I would start by repairing permissions on the drive.

If that doesn't help, I'd reformat the drive and re-create the Time Machine backup.

This sounds like a problem that could be caused by a partially damaged file system. I think it's a good idea to recreate the time machine backup every so often anyways.