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Newsgroups: comp.unix.bsd.freebsd.misc Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!munnari.OZ.AU!news.Hawaii.Edu!news.uoregon.edu!arclight.uoregon.edu!enews.sgi.com!news.sgi.com!sdd.hp.com!hpscit.sc.hp.com!news.dtc.hp.com!hplntx!hplb!hpcpb!jocko.bri.hp.com!aslater From: aslater@jocko.bri.hp.com (Al Slater) Subject: Re: dump and DAT, what block/density to use? Sender: news@bri.hp.com (News User) Message-ID: <E1wCE3.K1y@bri.hp.com> Date: Wed, 4 Dec 1996 15:58:50 GMT Reply-To: aslater@jocko.bri.hp.com References: <329E6BD7.5950@3-cities.com> <32A226A7.69F9@OntheNet.com.au> Nntp-Posting-Host: jocko.bri.hp.com Organization: Hewlett-Packard X-Newsreader: TIN [version 1.2 PL2] Lines: 39 Tony Griffiths (tonyg@OntheNet.com.au) wrote: : Mark Smith wrote: : > : > Greetings, : > : > I'm trying to use dump to backup a couple of file systems to a single : > 2G DAT tape. The problem is that it gets about 300MB into a tape and : > wants a new one. What block size and density options for dump should : > I use to get the full 2G of tape? : > : I use => # dump 0uBf 1000000 /dev/nrst0 /usr : ^ : | 1 million blocks should be enough but you might : want more depending on block size : For some reason, the 'standard' BSD dump doesn't seem to be able to : determine the size of the device but uses ~ 250 MB (ie. the size of some : very old streaming take) by default! FWIW, dump isn't terribly DC friendly. The problem goes something like.. the DAT/DLT/whatever compresses what you feed it. Depending on what you feed it, you might see marvellous amounts stored on tapes, or totally lousy amounts if its already compressed and going thru LZW again (and voila, it expands :-). So yep, you can fudge around it by telling it the device is huge.. you could also poke dump to ask the device about its current DC stats and how much it has already stored and work out some nominal amount you could possibly get on the tape.. If you're really disturbed by it, turn DC off and use a dump that knows about being told how many Kb you can put on the tape :-) ISTR that GNU dump does do Kb per volume/tape, I can't recall if 4.4 dump does ...UTSL I guess.. cheers, al (not speaking for HP...)