Date: Fri, 20 Aug 1999 16:30:49 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Christian Weisgerber <naddy@mips.rhein-neckar.de> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: Bizarre effect reading old tape Message-ID: <Pine.BSF.4.05.9908201630110.83055-100000@semuta.feral.com> In-Reply-To: <7pkc9u$btm$1@bigeye.rhein-neckar.de>
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You didn't say what drive you are reading it on. My guess is that if you're reading this on a 51000 that it is adding in the nulls, but I could be wrong. On 20 Aug 1999, Christian Weisgerber wrote: > I've been trying to read an old QIC-150 tape of mine. It was written > either on the Wangtek 51000 drive I use now or on an earlier Wangtek > 5525ES, I forgot. Under Linux. I have no idea what size blocks etc. > are on the tape. I use the unmodified quirk entry from CURRENT, > i.e. fixed/1024. > > After a "tar tv" stopped after the first couple of files, I transferred > the whole archive from tape to disk with "dd bs=20b". The result was > enlightening. There were 5k of data, followed by 5k of null bytes, > followed by 5k of data, and so on. I repeated the tape->disk transfer > with "dd bs=10b", resulting in 2.5k data, 2.5k nulls, 2.5k data, ... > Tried again with "dd bs=1k", and sure enough, now there were 512-byte > chunks of data interspersed with equally-sized chunks of null bytes. > Removing the interleaved null blocks produces an uncorrupted archive. > > I assume that this, er, unexpected behavior is somehow connected > to QIC-150 using 512-byte blocks. > > -- > Christian "naddy" Weisgerber naddy@mips.rhein-neckar.de > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-scsi" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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