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Time Machine seems to be deleting backups unnecessarily

Data (used / total) volumes are as follows:

Macintosh HD: 80 / 250GB (of the 80GB, 23GB is configured to be ignored by TM)

USB drive 1: 463 / 640GB

USB drive 2: Time Machine (see below) / 640GB

All drives are encrypted with FileVault 2. Some days ago I used TM to back up (afresh) my system disk. Then yesterday I plugged in my USB drive 1 and backed that up. The backup completed fine. Just now, TM informs me that it plans to backup the whole of the USB drive again and I have watched as it has deleted the backup that contained the data from USB drive 1. When i 'Enter Time Machine' I can see only the very latest backup from earlier today. I went into Console and checked the System Log for lines that cnotain 'backup' but cannot see anything that suggests a major error. Below is the output so far for this ongoing backup:

Jan 25 23:32:37 Amarantus.local com.apple.backupd[1811]: Starting manual backup

Jan 25 23:32:37 Amarantus.local com.apple.backupd[1811]: Backing up to: /Volumes/Chronos/Backups.backupdb

Jan 25 23:32:38 Amarantus.local com.apple.backupd[1811]: Forcing deep traversal on source: "Apollo" (mount: '/Volumes/Apollo' fsUUID: 3E7BB8EC-1E44-3A61-8E9A-BA1EB31B54F4 eventDBUUID: 119D0F0D-E532-41D6-AB2A-65BDA38F9856)

Jan 25 23:32:51 Amarantus.local com.apple.backupd[1811]: Deep event scan at path:/Volumes/Apollo reason:must scan subdirs|require scan|

Jan 25 23:32:51 Amarantus.local com.apple.backupd[1811]: Finished scan

Jan 25 23:32:53 Amarantus.local com.apple.backupd[1811]: Found 14709 files (463.78 GB) needing backup

Jan 25 23:32:53 Amarantus.local com.apple.backupd[1811]: 558.27 GB required (including padding), 126.79 GB available

Jan 25 23:32:55 Amarantus.local com.apple.backupd[1811]: Deleted backup /Volumes/Chronos/Backups.backupdb/Amarantus/2013-01-22-023427 containing 356 KB; 126.8 GB now available, 558.27 GB required

Jan 25 23:32:56 Amarantus.local com.apple.backupd[1811]: Deleted backup /Volumes/Chronos/Backups.backupdb/Amarantus/2013-01-22-013429 containing 356 KB; 126.8 GB now available, 558.27 GB required

Jan 25 23:32:56 Amarantus.local com.apple.backupd[1811]: Removed 2 expired backups so far, more space is needed - deleting oldest backups to make room

Jan 25 23:33:04 Amarantus.local com.apple.backupd[1811]: Deleted backup /Volumes/Chronos/Backups.backupdb/Amarantus/2013-01-21-181408 containing 17.2 MB; 126.82 GB now available, 558.27 GB required

Jan 25 23:33:04 Amarantus.local com.apple.backupd[1811]: Removed 3 expired backups so far, more space is needed - deleting oldest backups to make room

Jan 25 23:33:30 Amarantus.local com.apple.backupd[1811]: Deleted backup /Volumes/Chronos/Backups.backupdb/Amarantus/2013-01-22-003429 containing 202.3 MB; 127.03 GB now available, 558.27 GB required

Jan 25 23:33:30 Amarantus.local com.apple.backupd[1811]: Removed 4 expired backups so far, more space is needed - deleting oldest backups to make room

Jan 25 23:33:59 Amarantus.local com.apple.backupd[1811]: Deleted backup /Volumes/Chronos/Backups.backupdb/Amarantus/2013-01-24-115959 containing 463.05 GB; 590.08 GB now available, 558.27 GB required

Jan 25 23:33:59 Amarantus.local com.apple.backupd[1811]: Deleted 5 backups containing 463.27 GB total; 590.08 GB now available, 558.27 GB required

Jan 25 23:33:59 Amarantus.local com.apple.backupd[1811]: Backup date range was shortened: oldest backup is now Jan 25, 2013

Jan 25 23:35:08 Amarantus.local com.apple.backupd[1811]: Copied 17357 files (355.6 MB) from volume Amarantus HD.

Jan 25 23:55:45 Amarantus.local com.apple.backupd[1811]: Error: (-36) SrcErr:YES Copying /Volumes/Apollo/Lyre/Music/Bob Dylan/Desire/02 Isis.aif to (null)

I realise that with the extra space needed, the TM drive is well over half full, but for more than a year I have backed up a similar configuration continuously. It only registered a problem with capacity when, for example, I moved 200GB of data around on my USB drive. I have done nothing of the kind since it was last backed up successfully yesterday.

I can see that, having decided to backup the USB drive 1 again, TM needs to delete these existing backups, but I cannot figure out why it wants to back them up a second time anyway. I have not reconfigured the drive, changed encyptiuon parameters, etc. I should appreciate any thoughts re how I might investigate this further. Thank you.

MacBook Air, OS X Mountain Lion (10.8.2)

Posted on Jan 25, 2013 4:32 PM

16 replies

Feb 8, 2013 4:09 AM in response to Linc Davis

Thanks again, Linc. Thought I'd provide an update. When I used rsync (no disk image for I wanted to flush out the corrupted files) to copy data from the misbehaving source drive to a new target drive, I kept receiving the following error:

Feb 3 23:44:47 Amarantus kernel[0]: CoreStorageGroup::completeIORequest - error 0xe00002ca detected for LVG "Apollo" (A3619B17-9ABF-41DE-8E52-F8E32DACA169), pv D9E7EB85-2B5A-4846-95C7-ABF22444133D, near LV byte offset = 34265513984.

rsync copied all but 36 of around 13,000 files (these are recordings from CD so all replaceable). The Time Machine drive did not have any of the missing data because the previous backup had failed after it had deleted previous backups to make space for (unneceesary) large backup. Reformatted both drives using single-pass zero-out (I gather this enables the disk controller to identify and hive off bad blocks).

I now have the new drive with all my source data; reformatted Apollo has a snapshot of all my data (although I am not going to rely on this drive that was throwing errors); I am rebuilding my Time Machine backup on Chronos (encrypted; not to include the snapshot stored on Apollo).

I shall let you know if Time Machine starts kicking off unnecessary new backups at it had done originally (and which prompted this post). Again, thank you for your help above.

(By the way, to clarify and in response to your suggestion above, all external drives have been connected only directly to my MacBook Air - no hub.)

Time Machine seems to be deleting backups unnecessarily