Date: Tue, 21 Dec 1999 00:35:31 -0800 (PST) From: Matthew Jacob <mjacob@feral.com> To: Bob Bishop <rb@gid.co.uk> Cc: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>, freebsd-arch@freebsd.org, Stephen McKay <syssgm@detir.qld.gov.au>, Greg Lehey <grog@lemis.com>, Thomas David Rivers <rivers@dignus.com>, Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de>, Hauke Fath <hf@Melog.DE> Subject: Re: filemarks? Message-ID: <Pine.BSF.4.10.9912210029150.56276-100000@beppo.feral.com> In-Reply-To: <l03020907b484e67d59b9@[194.32.164.2]>
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> >> Whats wrong with this model? > > > >The user application cannot distinguish EARLY WARNING from hard EOT directly. > >You can put more data on tape after EARLY WARNING and before hard EOT. > > I'm not sure you can, in general [because not all drives will give you > sufficient warning]. The best you can guarantee is that closing the device > at this point will leave the tape in a state where a subsequent reader > won't get confused. EARLY WARNING is actually configurable for most SCSI drives. If you don't get EARLY WARNING (which is the EOM bit in sense data) associated with a plain old UNIT ATTENCTION sense key, you'll get a VOLUME OVERFLOW sense key (hard EOT). As far as I know you usually don't get EARLY WARNING detection on reads for these drives- this only happens on writes- I don't have my specs handy or I'd go back and make sure of this. The way I was specifying this is that subsequent reads aren't confused by this at all. If you miss EARLY WARNING (say the drive isn't strapped for it), you get VOLUME OVERFLOW (hard EOT) anyway on writes. -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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