Missing Time Machine Files caused by FSEvents Failure?

Question

I recently did a clean install/upgrade to Mac OS 10.8.2. I did a final update of my ongoing Time Machine Backup and verified Disk Integrity. After reinstalling and restoring my files, I have learned that some of my files and file changes are missing from the Backup.

One of the reasons for doing a clean install is that I have been having strange FSEvents failures for some time. If I would write a file from the terminal and then double-click that file in the Finder, I got a -43 File Not Found error until I reload the Finder window (leave and revisit that folder).

I believe Time Machine relies on the same FSEvents subsystem to detect file changes. Just as the Finder cannot see the new files, the Time Machine doesn't bother to back them up.

Can anyone confirm this theory? I need to better understand what is happening here so I can go about recovery. In other words, the data loss is silent, affecting an unknown subset of files, going back and unknown and possibly variable length of time. I am trying to diagnose the extent of the damage.

Answer 1

Yes.

It is known that FSEvents is the basis for Time Machine, and in fact Spotlight indexing as well before that.

In both cases, it acts as a tripwire for the relevant parts of your system, so that Time Machine knows what it needs to back up and Spotlight knows what it needs to index.

However, using FSEvents for backups does leave a tiny bit of room for error, as you have probably discovered. This old post from the Apple mailing lists details another idiosyncrasy.

Fseventer is a brilliant little app that can help you delve into the FSEvents world if you are interested.

At the end of the day, Time Machine isn't really considered professional-grade. It's brilliant for what it is, and I still use it, but I highly recommend pairing it with something like a weekly full disk clone (off-site if possible) for a more comprehensive backup strategy.