Date: Tue, 21 Dec 1999 12:27:57 -0600 From: Dan Nelson <dnelson@emsphone.com> To: Bob Bishop <rb@gid.co.uk> Cc: Stephen McKay <syssgm@detir.qld.gov.au>, Bruce Evans <bde@zeta.org.au>, Matthew Jacob <mjacob@feral.com>, "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>, freebsd-arch@freebsd.org, 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: <19991221122757.A71773@dan.emsphone.com> In-Reply-To: <3.0.6.32.19991221165541.007b7480@192.168.255.1>; from "Bob Bishop" on Tue Dec 21 16:55:41 GMT 1999 References: <Pine.BSF.4.10.9912211946160.11122-100000@alphplex.bde.org> <Pine.BSF.4.10.9912211946160.11122-100000@alphplex.bde.org> <199912211014.UAA21880@nymph.detir.qld.gov.au> <3.0.6.32.19991221165541.007b7480@192.168.255.1>
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In the last episode (Dec 21), Bob Bishop said: > On 1/2" tape, EOT was a reflective marker on the back of the tape. Still is :) We still process a couple dozen 9-track tapes a day here at work (3490s are getting more common), and have a lot of those sticky silver tabs lying around. > You were supposed to have something like 30ft of tape after the > marker, at least 10ft of which had to be writeable. So the drive > could complete the block being written at EOT, and still write two > tape marks thereafter (but data writes would fail IIRC). Only a > broken drive (not unknown) would let you run the tape off the reel. > ISTR (and you will appreciate this is a while ago) that drivers would > return the block size for the block written over EOT and zero for any > subsequent data write attempt. Closing the file wrote two tape marks. The documentation I have seen for my 6250 9-track drives implied that the warning marker meant you had room for the trailer on a standard-label tape, but you should really back up a few blocks before writing filemark + trailer + filemark anyway. I know when I wrote my tape program I could reliably write three or four 32k blocks after soft EOT before unspooling the reel :) -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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