On Thu, 6 Dec 2001 at 1:49pm, Stephen Carville wrote > My boss just asked me about redundancy in amanda. I explainmed to him > how the software distributes the full backups over the runspercycle in > an attempt to equalize the tape usage on each day's backup. He asked > me if a tape were lost or damaged how much of the data could be > restored? I don't really have answer to that one. > > Right now I have setup: > > dumpcycle 7 days > tapecycle 15 > runspercycle 5 > runtapes 2 > > Backups usually take one tape.
If each night's run goes onto one tape, then you *should* have three level 0s of every disk on tape at any point in time (since you have tapecycle=3*runspercycle). So, worst case, say that a tape goes bad that has on it the previous level 0 of a disk due again today. You could restore the level 0 prior to that (~two weeks old), and the 4 level 1s after that, which would get the disk to within a day of the lost level 0. You could then apply (probably by hand) the level 1s which occurred after the lost level 0. In that case, you'd only lose ~1 day's worth of data. For this reason, I *really* like having a tapecycle significantly larger than runspercycle*runtapes. If you find that you start actually using runtapes=2, it would probably be worth it to buy more tapes. Disclaimer: This is all of the top of my head, YMMV, void where prohibited, etc. -- Joshua Baker-LePain Department of Biomedical Engineering Duke University
