From owner-freebsd-scsi Sat Aug 21 10: 7:25 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from feral.com (feral.com [192.67.166.1]) by hub.freebsd.org (Postfix) with ESMTP id 9CF8914F64 for ; Sat, 21 Aug 1999 10:07:19 -0700 (PDT) (envelope-from mjacob@feral.com) Received: from semuta.feral.com (semuta [192.67.166.70]) by feral.com (8.8.7/8.8.7) with ESMTP id KAA07417; Sat, 21 Aug 1999 10:03:53 -0700 Date: Sat, 21 Aug 1999 10:03:52 -0700 (PDT) From: Matthew Jacob Reply-To: mjacob@feral.com To: Christian Weisgerber Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: Bizarre effect reading old tape In-Reply-To: <19990821154220.H16148@mips.rhein-neckar.de> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Sat, 21 Aug 1999, Christian Weisgerber wrote: > 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? > Put it in variable mode and see what happens- I suspect that the 'fake' variable that some QIC drives have might be at fault. = -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message