Large files / small backups on Debian LAMP

Backups on a LAMP server were much smaller than expected, and the cause was excessively large log files. This post explains the apparent paradox and the steps taken to trace and fix the problem.

The server in question runs the usual set of grandfather-father-son backups. Before each backup, the software prints the expected size of the backup into a log file. On other servers the estimate is usually bang-on. On this server, the backup turned out to be about 12 times smaller than the estimate. Not a problem in itself, but puzzling and indicative of something untoward on the system. Continue reading