Similarly to others, Time Machine made an excessively large .sparsebundle file (650GB) on my Seagate GoFlex drive, labeled .purgeable. Then Time Machine stopped backing up. Out of room. Purgeable file was never purged. Now I know to have at least twice the size of my original data available on the backup drive.
I wanted to delete the .sparsebundle. Manual file deletion didn't work; the "Deleting .sparsebundle" process went on for 6 days, ending with the extremely unhelpful [ The operation can’t be completed because the item “bands” is in use. ] Other forums suggested using Disk Utility or AirPort Utility to re-format; but neither app could see the wifi drive.
Only by going to the online GoFlex drive setup app was re-formatting finally a success.
https://www.seagateshare.com/ - log in as admin
Preferences > Administration > Storage Devices
Select the Hard drive, choose option Format and wait until it finishes. Even with a red error message, check the drive space result - mine worked anyway.
Presto - clean hard drive, all information erased as if unboxing for the first time.
'OSStatus error' may appear when you try to assign the drive in Time Machine. Unbelievably, setting up a secondary account via the GoFlex Home app fixes it.
GoFlex Home Agent > File > Open GoFlex Home > Preferences > Administration > New User
Just don't use any previous user account credentials and don't really ever use this to log on to the drive.
Voila. Drive ready to be re-assigned for Time Machine backup.
Credit where credit is due:
Sorry to those who don't want to re-format your drive. This solution is only good for returning the drive to zero. If you don't have a Seagate, but have a similar .sparsebundle Time Machine problem, perhaps your drive also has an online app re-format option at the manufacturer's site.