Date: Sat, 21 Aug 1999 10:03:52 -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.4.05.9908211001210.91597-100000@semuta.feral.com> In-Reply-To: <19990821154220.H16148@mips.rhein-neckar.de>
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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
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