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Path: sserve!newshost.anu.edu.au!munnari.oz.au!bunyip.cc.uq.oz.au!harbinger.cc.monash.edu.au!msuinfo!uwm.edu!daffy!uwvax!oka.cs.wisc.edu!jcargill From: jcargill@oka.cs.wisc.edu (Jon Cargille) Newsgroups: comp.os.386bsd.questions Subject: Re: Reading 8mm tape under FreeBSD 1.0.2 Date: 11 May 1994 15:06:01 GMT Organization: U of Wisconsin CS Dept Lines: 58 Message-ID: <2qqs8p$3ni@spool.cs.wisc.edu> References: <1994May10.045408.11205@ticipa.pac.sc.ti.com> NNTP-Posting-Host: oka.cs.wisc.edu In article <1994May10.045408.11205@ticipa.pac.sc.ti.com>, Rex Fowler <rmfowler@landru.mtc.ti.com> wrote: >AHA 1542CF SCSI adapter, FreeBSD 1.02. > >What steps should I have to perform in order to read a 2Gb 8mm tape >written in the following steps? > ># shutdown -r now (make sure tape drive is at defaults) ># tar cvf /dev/rst0 . (writes tape without problem) ># tar tvf /dev/rst0 (reads fine) ># shutdown -r now ># tar tvf /dev/rst0 (error, won't read tape) > st0: medium error, info = 10 (decimal) > I ran into the same problem when I first tried 8mm tape on FreeBSD. The solution is to explicitly set the blocksize to variable before you read it. Although after your reboot, "st -f /dev/nrst0 status" will report that the blocksize is "0" (or variable), it's sort of lying. When you first read from the drive, the SCSI driver (I think) actually tries to autodetect the blocksize, and gets it wrong. If you try the following instead, you should be able to read the tapes just fine: # shutdown -r now # st -f /dev/nrst0 blocksize 0 # tar tvf /dev/nrst0 At least, this works for me, and I thought my new tape drive was hosed until I figured it out... ;-) >I'm getting ready to install 1.1 but I want to be able to reliably >read my backups first. I've tried various things with "st" but I >can't find a sure-fire method to be able to guarantee the tape will >be readable. One other tip: If you're really making "backups", use dump/restore instead. dump/restore were created specificly for backups, and are better in a number of ways. They can restore an entire partition better, and have nice support for incremental backups. I also get fewer "stalls" from the tape drive when using dump/restore; tar stall constantly when writing small files... To be totally truthful, recent versions of gnu tar have support for many of the above features as well, but I still like dump/restore better. Is it just religious, or can someone else come up with other advantages of dump/restore? Hope this helps, Jon -- -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. Jon Cargille jcargill@cs.wisc.edu Want your .sig compressed? Reasonable rates and fast turnaround. Call today!