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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!munnari.OZ.AU!news.ecn.uoknor.edu!feed1.news.erols.com!howland.erols.net!vixen.cso.uiuc.edu!sdd.hp.com!col.hp.com!news.dtc.hp.com!hplntx!hplb!hpcpb!jocko.bri.hp.com!aslater From: aslater@jocko.bri.hp.com () Subject: Re: HP C1533A DAT tape ? Sender: news@bri.hp.com (News User) Message-ID: <E03118.Fo@bri.hp.com> Date: Wed, 30 Oct 1996 09:29:32 GMT Reply-To: aslater@jocko.bri.hp.com References: <stanbDzLuJv.CEo@netcom.com> <Dzrx1z.9xv@bri.hp.com> <54rce7$9ta@uriah.heep.sax.de> <stanbDzw2rz.6yz@netcom.com> Nntp-Posting-Host: jocko.bri.hp.com Organization: Hewlett-Packard X-Newsreader: TIN [version 1.2 PL2] Lines: 52 Stan Brown (stanb@netcom.com) wrote: : j@uriah.heep.sax.de (J Wunsch) writes: : >aslater@jocko.bri.hp.com () wrote: : >> : If I can, what device should I use ? Will this device enable : >> : the compresion on the tape drive ? : >> 1. hack st.c and put in relevant quirks / code to get yourself DC control : >> by device file used (code for this isn't hugely difficult) : >Ah, it's even simpler. :) : >Try the `mt comp 1' command. I've just checked, it's around there at : >least since FreeBSD 2.0.5. The man page still lies that it were not : >implemented though... but i cannot remember a single feedback whether : >it's actually working now. It has been implemented blindly after the : >SCSI-2 specs by Julian Elischer. : Well, since I have the hardware handy, I'll check it :-) Can : anyone think of a way to check to see whether the tape s really being : writeen with compression (assuming I don't have ahandy data set bigger : than the uncompressed tape size ? Would backing it up and trying to read : it on a non-compression drive work ? I have one of those at work, and I : seem to remember ocasianly geting read failures on tapes in it. : Whe I put these tapes in the comprresion mode drive the read OK. : Does this make sense ? Time it. Try backing up (assuming you are backing something thats moderately compressible) as is with the software compression on (mt command as above). Then try doing same with it off. Should be faster with on. You can also try.... play with the two dips underneath and see what speed you get. If you change the dips thus... 11 DC on by default, host control on 10 DC on by default, host control off 01 DC off by default, host control on 00 DC off by default, host control off Where host control on means that the host can ask to turn DC on/off in software. It should be noticeably different. There's a host of other stuff you could do like dinging the DC page and seeing what compression ratio you're getting, etc. regards, al (not speaking for HP..)