Original and backup do not match

[trevyn]

That's funny, I just noticed something similar, with a text file.

The first 2.5k (exactly 2560 bytes) of the file was completely missing in the backup, and at the end, an extra 2560 bytes were appended. Most were null bytes, but in the middle of those was the spurious string "/Applications/SuperDuper!.app/Contents/Resources/Copy Scripts"

Figure that one out. Copy logs show nothing abnormal.

Now, the interesting part is that I kept that text file open in BBEdit for some time. Any changes were very minor, no large parts of text were moved around, etc.

So my theory is it may have something to do with files that are open when the copy is performed. If so, how can we address this? Corrupt backups are public enemy number one.

Another possibility: this drive has a small handful of unrecoverable IO errors; in order to get backups to succeed, I had to exclude four media files (unrelated to this text file) using a...yes...Copy Script. This text file has never had a problem for me in normal usage, but is it possible that the first 5 blocks were unreadable at some point, and when they became readable again, the data was never copied over? Kind of shooting in the dark here. Are the historical logs for scheduled backups kept past the last one?