From owner-freebsd-questions@FreeBSD.ORG Tue Mar 15 15:32:23 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 98F7616A4CE for ; Tue, 15 Mar 2005 15:32:23 +0000 (GMT) Received: from smtp-out5.blueyonder.co.uk (smtp-out5.blueyonder.co.uk [195.188.213.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3519E43D4C for ; Tue, 15 Mar 2005 15:32:22 +0000 (GMT) (envelope-from xfb52@dial.pipex.com) Received: from [82.41.37.55] ([82.41.37.55]) by smtp-out5.blueyonder.co.uk with Microsoft SMTPSVC(5.0.2195.6713); Tue, 15 Mar 2005 15:32:57 +0000 Message-ID: <42370004.5060506@dial.pipex.com> Date: Tue, 15 Mar 2005 15:32:20 +0000 From: Alex Zbyslaw User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-GB; rv:1.7) Gecko/20040627 X-Accept-Language: en, en-us MIME-Version: 1.0 To: Ludo Koren References: <200503140938.j2E9c2EM024428@lk.tempest.sk> In-Reply-To: <200503140938.j2E9c2EM024428@lk.tempest.sk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 15 Mar 2005 15:32:57.0682 (UTC) FILETIME=[4396AB20:01C52974] cc: freebsd-questions@freebsd.org Subject: Re: Backup on DDS-4 tapes X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Mar 2005 15:32:23 -0000 Ludo Koren wrote: ># /sbin/dump -Lu0 -B 41943040 -C 32 -f /dev/sa0 /usr > > > I would guess that your tape drive does hardware compression in which case the amount of data which fits on a tape is variable. In such a case you can't tell dump how big the tape is -- I haven't used options like -B since 1600bpi reel-to-reel tapes, except in my day you specified how many feet of tape you had :-) from man dump -a ``auto-size''. Bypass all tape length considerations, and enforce writing until an end-of-media indication is returned. This fits best for most modern tape drives. Use of this option is particularly recommended when appending to an existing tape, or using a tape drive with hardware compression (where you can never be sure about the compression ratio). Don't know -L, must be a 5.x thing. Try: /sbin/dump -Lu0 -a -C 32 -f /dev/sa0 /usr I use -b 64 as well. Use cpio/tar at your peril as they may not do devices right and may not understand filesystem flags. --Alex