From owner-freebsd-scsi Sat Aug 21 9:35:45 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 93AA91503E for ; Sat, 21 Aug 1999 09:35:33 -0700 (PDT) (envelope-from 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 SAA25643; Sat, 21 Aug 1999 18:33:32 +0200 (CEST) (envelope-from naddy@mips.rhein-neckar.de) Received: by mips.rhein-neckar.de id m11IBPY-000WyPC (Debian Smail-3.2.0.101 1997-Dec-17 #2); Sat, 21 Aug 1999 15:42:20 +0200 (CEST) Message-ID: <19990821154220.H16148@mips.rhein-neckar.de> Date: Sat, 21 Aug 1999 15:42:20 +0200 From: Christian Weisgerber To: mjacob@feral.com Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: Bizarre effect reading old tape References: <7pkc9u$btm$1@bigeye.rhein-neckar.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93.2 In-Reply-To: ; from Matthew Jacob on Fri, Aug 20, 1999 at 04:30:49PM -0700 Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Matthew Jacob: > 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. Yes, I'm reading it on the 51000. I'm fairly sure that I've previously read that tape on the 51000 under Linux *without* inserted null blocks, so I think it can't be the drive alone. If I always got 512-byte chunks of data and nulls, that would be more plausible. But I always get contiguous data for half the read size. "dd bs=10k" does 10,240-byte reads. "mt stat" confirms that the driver is in 1024-byte fixed blocksize mode. According to sa(4), this should mean that each 10,240-byte read() is converted into a series of ten 1024-byte block reads. So why do I end up with 5,120 bytes of straight data followed bt 5,120 bytes of straight nulls? -- 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