I use Time Machine to create incremental backups to an external USB hard drive. Backups used to complete properly, but now Time Machine wants to backup much more data. Instead of the couple of GB of new data, the Time Machine menu bar icon popup menu reports it is going to backup 400+ GB! I stopped the backup as soon as I saw this to avoid filling up my backup drive. This is the relevant part of the backupd log:
18/05/15 21:05:06,778 com.apple.backupd: Starting manual backup 18/05/15 21:05:07,004 com.apple.backupd: Backing up to /dev/disk1s2: /Volumes/MacBackup/Backups.backupdb 18/05/15 21:05:15,385 com.apple.backupd: Will copy (22.3 MB) from Macintosh HD 18/05/15 21:06:04,176 com.apple.backupd: Will copy (Zero KB) from Data 18/05/15 21:06:04,225 com.apple.backupd: Found 761313 files (380.84 GB) needing backup 18/05/15 21:06:05,392 com.apple.backupd: 406.52 GB required (including padding), 904.71 GB available 18/05/15 21:06:48,246 com.apple.backupd: Copied 550 items (22.2 MB) from volume Macintosh HD. Linked 3201. 18/05/15 21:07:38,107 com.apple.backupd: Copied 123 items (1.57 GB) from volume Data. Linked 165. 18/05/15 21:07:38,738 com.apple.backupd: Backup canceled.
For some reason, backupd reports it will copy "(Zero KB)" from the Data partition (on an external eSATA hard drive). The output from
tmutil compare shows that less than 4 GB needs to be backed up:
Added: 3.6G Removed: 26.3K Changed: 292.2M
When ejecting the Data disk, Time Machine does backup the internal hard disk as it should (some tens of MB).
I have a feeling this could be related to the fact that the Data drive was not properly ejected one or more times. Disk Utility's "Verify Disk" reports no problems with the disk however. Also the backup disk is clean.
I think I ran into this problem once before, but then I didn't abort the backup. The backup drive filled up quickly to the point where no new backups could be made. The solution then was to erase my backup HD and configure it as a new backup disk (losing all existing backups).
How can I fix Time Machine to perform as before without having to erase the backup disk and start from scratch? I don't want to be forced to do this every couple of months.
UPDATE I haven't seen this behavior in a long time now. Perhaps it was a bug fixed in a macOS upgrade...