This has been bothering me for a while… I hardly change any files on my system, but every hour when Time Machine runs it somehow determines that 7 gigs of data has changed. Time Machine is ok for what it is, it’s biggest strength is probably ease of use. But it gives you no insight into what it’s copying exactly when it’s pushing gigabytes of data to my network backup.
As it turns out, there’s a handy little tool that tells you exactly what’s changed with your latest backup.
Timedog will tell you exactly which directories were backed up and how much data they represented. For me, the culprit turned out to be my Thunderbird mail client. It stores all email for a mailbox into a single flat file, and some of my mailboxes are gigabytes in size. Every new message I receive is causing the entire mailbox to get backed up again, eating up all my available backup storage pretty quickly.
Now that I figured it out, fixing this was pretty easy: simply put an exclude filter in Time Machine preferences to ignore any changes in my Thunderbird folder. All of my email is stored in my Gmail so it’s already in 2 places anyway.