Date: 20 Aug 1999 22:03:10 +0200 From: naddy@mips.rhein-neckar.de (Christian Weisgerber) To: freebsd-scsi@freebsd.org Subject: Bizarre effect reading old tape Message-ID: <7pkc9u$btm$1@bigeye.rhein-neckar.de>
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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
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