Date: Wed, 15 Mar 2006 10:03:46 -0500 (EST) From: Jerry McAllister <jerrymc@clunix.cl.msu.edu> To: xfb52@dial.pipex.com (Alex Zbyslaw) Cc: freebsd-questions@freebsd.org Subject: Re: dump level 9 Message-ID: <200603151503.k2FF3kUG027643@clunix.cl.msu.edu> In-Reply-To: <44182470.5060902@dial.pipex.com>
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> > Jerry McAllister wrote: > > >But, I wonder why you chose level 9 for your change dumps. It sort > >of defeats the system. It would be more normal to use level 1. > >I know that [some much] earlier versions of BSD dump only took levels > >up to 5, but I presume that since they include up to 9 in the documentation > >it should work. > > > > > If you only use one level other than 0, then it makes no difference what > that level is: 1, 9, 5 anything but 0. A level N dumps everything since > the last dump < N, which in this case is always the last level 0. Of course, but then you limit yourself from moving to a level 2 or higher to accomodate an especially large change dump the day before. > Using "modified tower of hanoi" (so the man page says :-)) can decrease > the amount of data per dump at the cost of having to do more dumps: e.g. > I do 0: 1 3 2 1 3 2 ... 0 ... But if I have to restore everything and > the last dump was a 2, I have to restore the 0 1 and 2. Similarly if it > crashed after 3, I would do 0 1 3. That cuts down the amount of data > dumped, but is slightly more complex than just having to restore the 0 > and last 9 (in the OPs case). I could use 1 7 9, or 4 6 8 instead of 1 > 2 3 and the data dumped would be the same in each case. The simplest, if you do a weekly full dump and daily change dumps is 0, 1, 2, 3, 4, 5, 6 but of course, that mean doing the most restores, though possibly smaller ones, of all the schemes. It doesn't work, of course, if you only do a monthly full dump and daily change dumps. > I was pretty sure that BSD 4.2 had 9 incremental dump levels, but that > was long, long ago in a universe of 1600bi tapes far, far away :-) I don't know just when it was, but back then I was working on vendor's proprietary flavors of BSD, so it could have been their particular flavor, although I am pretty sure they just took utilities like dump and simply recompiled and used them as is. ////jerry > > --Alex > >
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