You're right, but you can use LVM to solve that problem: make an LVM snapshot, run your backup solution (eg, rsnapshot) on the LVM snapshot, remove the LVM snap

You're right, but you can use LVM to solve that problem: make an LVM snapshot, run your backup solution (eg, rsnapshot) on the LVM snapshot, remove the LVM snapshot. You still have the problem of caches and transient data, but all files will share the same point in time. In my experience LVM snapshot performance is good, you can even make it small and let it grow to track the changes while you backup is running. EDIT: actually rsnapshot has LVM snapshot support (since version 1.3.1 from Aug 31, 2008), so there you are.