Time Machine backups fail repeatedly with an "Unable to complete ..." message whenever iTunes is transmitting (wired) to my Airport Express.

Thanks for your tip. I thought you would like some feedback.

After performing a full reset of Time Machine, my system ran several backups without any problem. But within about four hours, it once again was unable to complete backups.

A few minutes ago, I used the Disk Utility app to check my Toshiba backup drive (purchased a few days ago) which indicated that there might be a problem (message was very vague). After running "repair," backups again seem to be working.

For what it's worth, simply using iTunes to play music never caused any problems with Time Machine. Time Machine, however, would fail 100 percent of the time whenever it attempted to run after I had used iTunes to import a CD. I could get Time Machine to work again, however, by rebooting the system after which it would run two or three times then once again fail with the "Unable to complete" message.

More specifically, when Time Machine fails, the error log typically reports "error 11" and "error 22" as shown below:

Feb 6 02:07:31 Bill-Wilkens-iMac com.apple.backupd[1106]: Backup failed with error: 11

Feb 6 03:07:24 Bill-Wilkens-iMac com.apple.backupd[1106]: Error: (22) setxattr for key:com.apple.backupd.HostUUID path:/Volumes/Backup/Backups.backupdb/Bill Wilken’s iMac size:37

Bill

After one successful backup ....it's failing again with the above message in the error log.

I'm beginning to think that there is some type of problem with my new 1TB Toshiba drive.

A few hours ago, I reattached my old 0.5TB Toshiba drive and backups are working perfectly. Later today, I'm going to reattach the 1TB drive and attempt to perform a mass copy of my iMac drive to the Toshiba. If everything copies without fault, then I think it is probably safe to assume that there is really nothing wrong with the drive, but that there is some type of glitch in Apple's OS or Time Machine software working with that particular make/model drive.

Will keep you posted.

I thought for a moment that my Time Machine problem was solved. After reformatting my external 1TB Toshiba drive, backups ran flawlessly for three or four hours. Once again, however, they have died.

Looking at the error log, it appears that the source of the problem may be folder permissions in \Library (which I never have touched). See, for example:

Feb 6 18:07:07 Bill-Wilkens-iMac com.apple.backupd[1638]: Error: (22) setxattr for key:com.apple.backupd.HostUUID path:/Volumes/Backup/Backups.backupdb/Bill Wilken’s iMac size:37

Feb 6 18:07:17 Bill-Wilkens-iMac com.apple.backupd[1638]: Backup failed with error: 2

Interestingly, The Colorpickers folder grants Me read & write permissions, but everyone else has "No Access." I presume that this includes system applications like Time Machine.

When all is said and done ... your assertion that there is something wrong with the drive doesn't square with the fact that I've been able to use Apple's Disk Manager to write zeroes to the entire drive for the last several hours without a single write fault. If there were something wrong with the drive physically, this sort of formatting ordinarily would fail.

For what it's worth, Time Machine can write without any problems to my old 0.5TB Toshiba drive, just not to the newer 1TB drive. Time Machine, however, can always write successfully to the new ! TB drive immediately after a cold boot. Which makes me wonder whether the problem has something to do with hardware and/or software caching.

In any event, I'm done with this drive. It's going back to the store tomorrow morning.

Thanks for all your thoughtful comments. It's nice to see that the Apple world is beginning to develop the helpful culture that I've enjoyed for many years with Linux.

I think I've found the answer ... apparently Toshiba's 1TB drives have a nasty habit of "going to sleep" ... which would explain a lot. See snippet below reported in http://t3chnot3s.blogspot.com/2010/03/toshiba-1tb-usb-drives-and-using-apple.htm l

Toshiba 1TB - Sleep Issue

I was doing something like this with an external Toshiba USB/SATA II drive – but this proved futile and frustrating as the Toshiba USB/SATA drives have a tendency to sleep at random (if you don't believe me, just search Google) – which is not a good thing for iTunes and especially for iPods/iPhones since anything iTunes cannot find it will subsequently remove from the iPod/iPhone (including apps and movies as well as music). Not to mention, this was only an external drive solution and not network attached (you'll see where I'm going with this part later).

After doing much research, I found the sleep issue was just not resolvable!