From owner-freebsd-scsi Fri Aug 20 15:34:46 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from news-ma.rhein-neckar.de (news-ma.rhein-neckar.de [193.197.90.3]) by hub.freebsd.org (Postfix) with ESMTP id 3903815245 for ; Fri, 20 Aug 1999 15:34:42 -0700 (PDT) (envelope-from bigeye.rhein-neckar.de!naddy@mips.rhein-neckar.de) Received: from mips.rhein-neckar.de (uucp@localhost) by news-ma.rhein-neckar.de (8.8.8/8.8.8) with bsmtp id AAA14373 for freebsd-scsi@freebsd.org; Sat, 21 Aug 1999 00:33:51 +0200 (CEST) (envelope-from bigeye.rhein-neckar.de!naddy@mips.rhein-neckar.de) Received: by mips.rhein-neckar.de id m11HuqG-000WyUC (Debian Smail-3.2.0.101 1997-Dec-17 #2); Fri, 20 Aug 1999 22:00:48 +0200 (CEST) From: naddy@mips.rhein-neckar.de (Christian Weisgerber) Subject: Bizarre effect reading old tape Date: 20 Aug 1999 22:03:10 +0200 Message-ID: <7pkc9u$btm$1@bigeye.rhein-neckar.de> To: freebsd-scsi@freebsd.org Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org 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