Time Machine weirdness...

I've been using Time Machine to back up to an external 400GB drive. It's worked fine for months, but stopped backing up a few days ago.

After each attempted backup, it now gives me an error dialog stating the size of the backup will exceed the amount of space on the external drive. The problem is that a) it vastly overstates the size of the backup (by over 200GB); and b) it vastly understates the available space on the external drive.

I've gone so far as to completely erase the external drive, figuring I'd just start the Time Machine deal over from scratch. No dice. It's still giving me the same trouble.

Any ideas?

Ken

That's really weird. Especially if you reformated the drive and started Time Machine over from scratch.

Is the drive partitioned or is the whole 400gb available for Time Machine?

How big is the HD you are trying to back up?

Are you using Aperture, Microsoft Office, or Parallels/Fusion? Is Time Machine backing up any of these? They all have compatibility issues with the way Time Machine performs backups, although I'm not sure how they would cause this exact problem.

The drive is not partitioned. The whole formatted capacity is available to TM.

The drive I'm backing up has about 372GB used. Clearly, this TM drive is not a long term solution, but I had over two months of incremental backups on it before it stopped working.

I do have Office, though it's never caused a problem before and no changes have been made to it. I've got Aperture installed, though I mostly use iPhoto and, like with Office, no problems have been experienced. I did install Fusion last week and have now uninstalled it, but got the same result.

At least TM is now correctly stating the available space on the backup drive, though it's still overstating the needed space by about 50GB. See the attached image of the error dialog.

Any other thoughts?

Ken

I would guess that the problem lies in the ratio of the size of the backup drive to the size of the things you are backing up. Making the Time Machine backup smaller would probably help.

Exclude your Aperture Library. Exclude your Microsoft Identities Folder. Exclude anything related to Fusion if it still resides on your hard drive. You cannot count on TM to back these up reliably anyway. This will reduce the amount of space TM needs.

And as a quick test, temporarily exclude a couple other large folders (whatever is taking up 300gb), reformat TM, and then try the backup. This should tell you if it's simply a matter of not enough free space on the HD.

If it doesn't clarify what the problem may be, then no harm done--just 'unexclude' the folders.

OK, that seems to have done it. I excluded a number of large folders, eventually getting the backup down to about 190GB. It's currently backing up properly.

I actually tried excluding a few things yesterday, but either I didn't exclude enough, or Fusion was still interfering (I uninstalled it this morning), or both. I'll unexclude my large folders one at a time and see what I can get away with before it chokes TM again. Clearly, a much large backup drive is in my immediate future.

Thanks for the help!

Ken

My mother in law has so much furniture in her living room it makes me claustrophobic. I always tell my wife I wish she would get rid of some of those chairs so that there would be somewhere to sit.

TM is the same way--just because you can physically stuff the entire backup on the drive, doesn't mean that it's going to fit well. Not only does it need storage space, it also needs space to move stuff around.

I hear you loud and clear. You'd think that after 30+ years in computers, I'd have known better...

A bigger drive will be ordered shortly!

Ken