Bill Hudacek writes: > One small note, if I may...I'm not sure about others' thoughts on this > matter, but I shared your "OMG" moment, Travis :-) > > When I discovered BackupPC, I was very pleased with it. I still am, > lest anyone think otherwise! > > However, I was very dismayed to find the word "incremental" being used > to describe the backups performed between full backups. it's pervasive > throughout the docs, FAQs, and this news group. > > As a (former, in a past life) UNIX systems manager for an international > corporation's data center in the U.S., I dealt with these kinds of backups: > > 1. Full > 2. Differential > 3. Incremental > > A differential the day after a full would backup only those files that > changed that day. A differential the day after that would back up all > files that had changed since the full backup - in other words, the > contents of the first day's differential backup was included in the > second day's backups. This was not as bad as it sounds, as a file > deleted before the backups on day 2 would still appear on day 1's > differential backup. > > Incrementals, however, meant only files changed since the last backup > "of any kind" (full, differential, incremental) would be backed up. > > Thus, incrementals were by nature very constant in terms of execution > time and storage media consumed. When you have hundreds of big-iron > servers with local disk, SAN space, and NAS space, the difference > between incrementals and differentials can be huge (in terms of runing > time and space required). > > I'm not even speaking as a UNIX guy here, this operational approach was > used for PCs and VAX VMS boxen too. > > I would have been happiest with a three-tiered backup model in backuppc, > as my use of an "on-line backup server" means having 1 full, the latest > differential (say, from "full + 3 weeks"), and three incrementals to > restore is not an inconvenience at all. Back when we used "tape sets" > (RAID-5 arrays of tape drives), we had to find all the media and request > that they be brought back on-site. Thus, we did differentials once per > week so we did not have dozens or hundreds of tapes to restore. At most > we needed full backup set + one differential set + max # of incremental > sets since the last differential. > > However, having said that - with my BackupPC environment, instead of > running a full backup once a month, and having differentials weekly, > with incrementals daily, I simply run fulls weekly and thus the > "differentials" that backuppc calls "incrementals" do not ever approach > the cost of a full backup (which I would consider not just an > inconvenience but a serious problem).
In the spirit of dump(1), incrementals in BackupPC are all level 1 (ie: refer back to the previous level 0, or full). A yet-to-be-implemented feature is multi-level incrementals. The goal would be to allow the level of each incremental to be configured. This would give you the flexibility to support (in your terminology) full, differential and incremental backups. Craig _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/backuppc-users http://backuppc.sourceforge.net/
