Hi Stefan, ----- Original Message ----- From: "Stefan G. Weichinger" <[EMAIL PROTECTED]> To: amanda-users@amanda.org Subject: Re: Meaning of "bump" Date: Sat, 15 Jan 2005 12:08:31 +0100
> OK, it says: > > > The minimum savings required to trigger an automatic bump from one > > incremental level to the next. If AMANDA determines that the next > > higher backup level will be this much smaller than the current > > level, it will do the next level. > > I see that bump->bump-thing ... will correct that. yes, that's what i meant > The basic goal of using these parameters is avoiding too much > incremental backups happening too fast. > > As it gets harder to restore from a backup-set with lev4 or similar as > you have to use 5 tapes to get your full data back, you want to avoid > lev4 and just go to lev2 or lev3 ... > > So you want to get some benefit from BUMPING to lev2 (which actually > means the switch from level n to level n+1) after you are already on > lev1, and this benefit should be saving tapespace because that lev2 > backup is smaller than the lev1. that's exactly what i would like to read in the docs (Bumping means switching backup levels or so). > Now read again: "If AMANDA determines that the next higher backup level > will be this much smaller than the current level, it will do the next > level." i understand this in the context you gave - but i was completely unsure about it when i read it for the first time. please don't take it too serious - i simply think that people enjoy reading the docs more when this is clearer. > If size_of_lev(n+1) - size_of_lev(n) > bumpsize, then AMANDA decides > to do the lev(n+1), because the savings in space are worth it. > > Not enough with this, there is also bumpmult ! > > Actually it's: > > threshold = bumpsize * bumpmult^(level-1) > > This introduces a somewhat exponential behavior, bumping from lev2 to > lev3 should be harder than bumping from lev1 to lev2, as you want to > avoid high backup-levels. > > There is also "bumpdays" to keep the lev down as well. > > --- > > This as a quick-n-dirty-explanation, hope this helps. perfectly - that's what i was looking for :-) thanks, Kai