Open Radar

 
Summary: I've encountered this problem 2 or 3 times over the past year or two—it seems clear at this point that it's not just a fluke. Please see the attached files which help illustrate the problem. In backupd.log you can see that there are various entries like "Backup completed successfully". I also keep the Time Machine menu bar icon in my status bar, and I can see that it is regularly doing something. If I click on the icon it will say "Backing up…" quite often.

The problem is, it is completely failing to actually back up any changed files. It creates a new directory in Backups.backupdb with the appropriate date and time, but the files inside do not change from the previous backup. In this particular case it has not backed up any changes since April 16th, and it's now April 27th.

In the screenshot "Current Files", you can see one file that was last changed April 17th, 10 days ago. In the screenshot "Latest Time Machine Backup", you can see the same file, in a backup made one hour ago. Except this is not the latest file—this version was last changed 3 months ago. Basically it's creating new backups that are frozen in the same state they were April 16th.

Steps to Reproduce: I have no idea, but I can tell you my setup:

- Main computer is a 13" MacBook Air with 10.7.3
- I have a headless Mac mini with 10.7.3
- Connected to the Mac mini is the Time Machine drive, a 6TB My Book Studio Edition II connected via USB
- The Air backs up over Wi-Fi, along with my wife's 11" Air
- The Mac mini also backs up to that drive, over USB
- Most of the time my Air is connected to a display on my desk. But it does get unplugged frequently, and sometimes it's unplugged and off the local network for days if I'm out of town.

Expected Results: When Time Machine backs up, it should actually back up any files that have changed. If it is unable to for some reason, I should get an error.

Actual Results: Time Machine acts as though it is backing up successfully even though it is not.

Regression: Unknown

Notes: One thing worth noting in the log files in the message "Copied 21 files (33 bytes)" This doesn't seem to match up with the previous message "100.0 MB required (including padding)". If I intentionally create a large file and run a backup, I get "683.0 MB required (including padding)"… followed by the same "Copied 21 files (33 bytes)" So it seems to be getting confused about what needs to be backed up.