On 4/24/2014 3:52 PM, backu...@kosowsky.org wrote: > Bowie Bailey wrote at about 14:38:26 -0400 on Thursday, April 24, 2014: > > Think of incremental backups this way... > > > > Pros: > > 1) They finish running quicker. > > > > Cons: > > 1) They can miss backing up files in certain circumstances > > 2) They cause the same data to be transferred multiple times. > > - Each incremental will transfer all the same data as the previous > > one plus any new changes > > - The next full backup will also need to transfer all of that data > > again. > > Not quite. > > Only data changed/added since the previous level incremental needs to be > transferred.
True, but I was trying to keep things fairly simple. Besides, I don't think I've seen an example of a situation where multiple levels of incrementals were needed in BackupPC. > So technically, if you have infinite levels of incrementals, then > each changed/new file is transferred only once so there are no extra > transfers beyond what all fulls would require. > > In reality, you want to have a limited number of levels (cycling back > to the full), since having more levels of incremental will cause > reconstruction of the latest backup to take longer since all the > previous levels back to the full need to be scanned -- in particular, > all the attrib files need to be read to see what files may have been > deleted... This reconstruction is needed not just when you restore but > every time you back up so that changes can be identified. In > particular, it is *not* sufficient to just look at the previous > incremental level to determine what files have changed. And if the incrementals were dependent on each other, you would have to keep *all* of those incrementals. None of them could ever be deleted without losing information. This would cause your pool size to continuously grow since deleted files would never be removed. > The bottom line remains the same. If your bottleneck is bandwidth, > then do all fulls. Exactly. -- Bowie ------------------------------------------------------------------------------ Start Your Social Network Today - Download eXo Platform Build your Enterprise Intranet with eXo Platform Software Java Based Open Source Intranet - Social, Extensible, Cloud Ready Get Started Now And Turn Your Intranet Into A Collaboration Platform http://p.sf.net/sfu/ExoPlatform _______________________________________________ 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/