2009/1/16 Dominic <[email protected]>: > Michael Biebl wrote: >> >> Hi, >> >> I'm new to this list, so if this question has already been answered >> please bare with me and point me to the relevant discussion. >> >> I was wondering, if rdiff-backup stores the snapshots differentially >> or incrementally >> > > incrementally >> >> Say, I create a snapshot every day. >> If I want to restore a file from 15 days ago, do I need all 15 >> snapshots to restore the state (incremental) or only the current >> up-to-date state + 1 rdiff (differential)? >> > > you need them all, but rdiff-backup handles it all 'under the hood' >> >> If rdiff-backup only allows incremental backups, I see the following >> problems: >> 1.) If a file changes a little every day (big mysql db), then >> restoring the file (from say 100 days ago) will probably take a lot of >> processing time, space and memory. >> > > the extra overhead in space for many incremental backups vs. one > differential backup is not great, but yes I guess it will take more time and > memory
Does anyone have any first-hand experience with such a scenario (say a several GB big mysql db, which basically changes every day)? >> >> 2.) If one of the rdiffs goes corrupt (e.g. via a bad sector), all my >> older backups are broken. >> > > hmmm, true I think, you should use raid or (better IMHO) a secondary backup > (use rsync). Is there a reason why you recommend rsync for that? If I understood the project description correctly, rdiff-backup should work just fine for remote backups. Are there any (dis)advantages to rsync? There is also the --verify-at-time option in rdiff-backup which > I confess I have not used (oops!) - this should allow you (I think/hope) to > confirm that backups at any given point in the past are not corrupt. Good > idea to run this before doing the secondary backup I guess? [Question for > expert: if rdiff-backup --verify-at-time 1Y succeeds does this also mean > that all backups within the last year are uncorrupted too? I see that it > reports success even if there are no backups that old in the archive.] >> >> 3.) I can't throw away rdiffs, say I want to create daily snapshots, >> keep 30 of them, then keep monthly snapshots, and so on (basically >> what tools like rsnaphost provide). >> > > The logic of rdiff-backup is that you don't need to try to keep just monthly > snapshots, you can keep your daily snapshots forever. It is true that > recovering a file from a very long time ago, and which has changed a lot in > the meantime, might take a while, but it would be a very rare event. > Recovering more recent files which would be a more common event would be > much faster, and of course the most recent backup (which is probably what is > wanted in 95% of cases) is stored in the clear. Again, does anyone have any first hand experience (and numbers) for say a sever with a typical lamp stack (everything is backuped) > Others may have some better informed comments... Thanks for your comments so far. Cheers, Michael -- Why is it that all of the instruments seeking intelligent life in the universe are pointed away from Earth? _______________________________________________ rdiff-backup-users mailing list at [email protected] http://lists.nongnu.org/mailman/listinfo/rdiff-backup-users Wiki URL: http://rdiff-backup.solutionsfirst.com.au/index.php/RdiffBackupWiki
