Backup statistics - using HAMMER on my LAN backup box

[Michael Neumann]

Matthew Dillon wrote:
>     HAMMER is stable enough now that I am able to run it on my
>     LAN backup box.  I'm using it to test that the snapshots work
>     as expected as well as to test the long term effects of reblocking
>     and pruning.  The LAN backup box NFS mounts all the other boxes 
primary
>     partitions and uses that to create a daily snapshots from 5 machines
>     (apollo, crater, leaf, pkgbox, and my office workstation), covering
>     around 90G of backed-up data.  The box mirrors the latest daily
>     snapshot off-site once a week so I can afford to lose the data if
>     I hit a bug.

I am wondering how you exactly do the backup. You probably just copy
over the modified files, right? But how do you determine which files
have been modified? Do you use some md5 checksum (which is expensive!)
or just the mtime?
Would be even better to use something like rsync, right?

Regards,

  Michael