Jim Wilcoxson wrote at about 14:10:31 +0000 on Thursday, June 9, 2011: > Boniforti Flavio <flavio <at> piramide.ch> writes: > > > > > Hello to both of you, Adam and Andrew. > > > > > Great suggestion, backing up the VM's as if they were normal > > > clients... > > > > That's an option I can't afford to implement. I've been asked > > *explicitly" to backup the images itselves! > > > ... > > > > Indeed, the splitting would be OK, but still: I'm in need of backing up > > a *big file* which may change in some bytes... > > Hi Flavio - I'm developing a "push" backup program, HashBackup, that will > backup > a VM image at around 20MB/sec for changed data and 40-50MB/sec for unchanged > data using dedup. This is on a Macbook 60MB/sec hard drive. You could > attach a > USB disk, backup to that, and also send the incrementals offsite. > Incrementals > will be minimized to the actual disk blocks that changed. > > Rsync usually doesn't work that well with VM images because by default it > uses a > block size of sqrt(filesize). For large VM images, the block size becomes > very > large. VM images often have lots of scattered small changes, defeating > rsync's > delta algorithm.
Just as an FYI, BackupPC uses a more limited blocksize range that does not get that huge. In fact, the block size ranges from 2048 to 16384 with the values within the range set by int(file_size/10000). > In contrast, HashBackup uses 4K blocks for VM images, which minimizes the > size > of the incremental. You could also do this with rsync by specifying the > block > size, and I think BackupPC may force a block size of 2K (sometimes?), but > rsync > doesn't have efficient data structures for handling this with huge VM image > and > just goes CPU bound. > > If you want to try it, the beta site is http://www.hashbackup.com > > Basically, you would do: > > $ hb init -c /mnt/usbdrive/vm1 > $ hb backup -c /mnt/usbdrive/vm1 -D1g ~/Documents/VMImages/vm1 > > Using 1gb of RAM, HashBackup can dedup a 128GB VM image. > > Jim > > > ------------------------------------------------------------------------------ > EditLive Enterprise is the world's most technically advanced content > authoring tool. Experience the power of Track Changes, Inline Image > Editing and ensure content is compliant with Accessibility Checking. > http://p.sf.net/sfu/ephox-dev2dev > _______________________________________________ > 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/ ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ 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/
