On Thursday 29 April 2010 13:44:52 Tyler J. Wagner wrote: > I use local rsync for backing up the server itself (indeed, for about 70 > servers), and it has always been fine for me. I don't think the > checksumming really makes much difference, as once it is copied (to > itself) it will still have to be checksummed to go into the pool.
Yeah, but the rsync protocol's chunk checksumming is designed to reduce network traffic, and since in the case of a localhost backup the bandwidth is however many orders of magnitude higher than over a network, it's just going to waste CPU cycles, isn't it? I know that when used to sync two local directories, rsync proper will enable --whole-file by default for this reason. However, because RsyncP is involved, I doubt rsync will be aware that it's a local transfer, so the option would have to be specified explicitly. > Is the checksum caching rsync does the same as the checksum that is stored > in the pool? No, it's a different hash. My understanding is that under defaut RsyncP conditions, BackupPC will do two pooled file decompressions, plus a checksum for each chunk of the file, plus a whole-file checksum, for each file. Checksum caching prevents all of this CPU overhead, but does not affect BackupPC's pool- related checksumming. BackupPC will still perform file content hashing and filename mangling regardless. Here are the docs on checksum caching for reference: http://backuppc.sourceforge.net/faq/BackupPC.html#rsync_checksum_caching Paul ------------------------------------------------------------------------------ _______________________________________________ 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/
