Comment 3 for bug 1256300

You've to divide it by 256 (don't ask me why, I've no clue) so you will get rsync return code 24:
> 24 Partial transfer due to vanished source files

One or more files changed before rsync could transfer them. Rsync will transfer them next time again. You can browse the snapshot log to see which files where effected. But normally you don't need to worry about it.

Only if those files is a db (MySQL, Postgres, ...) you should rather exclude the files, create a db dump with custom user-callback script and backup only the dump.