-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Msquared wrote: > On Sun, Sep 28, 2008 at 08:02:56AM -0400, Andrei Stebakov wrote: > >> Now it looks like every incremental backup is not different from a full >> backup as it takes almost the same space on disk as a full backup. I >> thought it should only backup the delta... > > I think that while a delta is backed up, BackupPC then uses hard links to > the files from the last backup in order to fill out the backup so that it > looks like a full copy. > > I also think this is part of BackupPC's pooling mechanism.
When a backup is in progress, (an incremental using rsync) rsync reports the file has changed, so it copies the old file into backuppc/pc/<hostname>/<num>/<directory>/<filename> It then updates this file with the changes. Once the complete backup has finished for this host, then the backuppc_link process runs through the files and hard links backuppc/pc/<hostname>/<num>/<directory>/<filename> to backuppc/pool/<hash> Thus, if you do a du -s backuppc/pc/<hostname>/<num>/ you will get the full size of the backup, however (on linux, in my experience) if you do a du -sm backuppc/pc/<hostname>/1?? it will show something like this: 323545 backuppc/pc/<hostname>/100 112 backuppc/pc/<hostname>/101 105 backuppc/pc/<hostname>/102 This shows that the first backup used 323545M of space, while the next one only used 112M because most of the files are sharing the same space on disk, hence du doesn't double count them. > For comparison, I theoretically have 1terabyte of data backed up, but it's > actually only consuming about 120-130gigabytes of storage on my backup > server, thanks to BackupPC's data pooling. Yep, exactly, the files are only stored in the pool but are hard linked into each of the host/backup directories where they are needed. Regards, Adam -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFI7dUeGyoxogrTyiURAgguAKDTJgYUEPwcJu4e20T2Z6CKA1iGnwCgqXsx 6kuw9GCqzi4QGlotUGp3MhQ= =BBs+ -----END PGP SIGNATURE----- ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
