From owner-freebsd-hackers Sun Apr 21 08:57:27 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id IAA23592 for hackers-outgoing; Sun, 21 Apr 1996 08:57:27 -0700 (PDT) Received: (from jmb@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id IAA23586 Sun, 21 Apr 1996 08:57:25 -0700 (PDT) From: "Jonathan M. Bresler" Message-Id: <199604211557.IAA23586@freefall.freebsd.org> Subject: Re: Archive Anaconda To: dkelly@hiwaay.net (David Kelly) Date: Sun, 21 Apr 1996 08:57:25 -0700 (PDT) Cc: peter@taronga.com, hackers@freebsd.org In-Reply-To: from "David Kelly" at Apr 21, 96 10:24:09 am X-Mailer: ELM [version 2.4 PL24] Content-Type: text Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk David Kelly wrote: > > I wonder if tar and/or dump and/or dd default to the 512 byte blocksize > reported by mt? Tried a simple "dd if=/dev/tape of=/dev/null" and the tape > hunted back and forth, back and forth. But when I added "bs=10k" is spooled > all the way thru the tape. > > How do we determine what blocksize a tape was written with? > tar uses the native blcksize of the device. dd defaults to 512 byte blocks dump defaults to 10240 bytes per record in 10 blocks ;) there is an interblock gap (ala interframe gap on the network-- no stones, please.) between the records/blocks. the gap is needed but its just dead tape. a larger block size minimizies this wastage. Jonathan M. Bresler FreeBSD Postmaster jmb@FreeBSD.ORG FreeBSD--4.4BSD Unix for PC clones, source included. http://www.freebsd.org/