From owner-freebsd-current@FreeBSD.ORG Sat Apr 24 09:06:31 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 17F9216A4CE; Sat, 24 Apr 2004 09:06:31 -0700 (PDT) Received: from saturn.criticalmagic.com (saturn.criticalmagic.com [68.213.16.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id 585C143D3F; Sat, 24 Apr 2004 09:06:30 -0700 (PDT) (envelope-from richardcoleman@mindspring.com) Received: from mindspring.com (titan.criticalmagic.com [68.213.16.23]) by saturn.criticalmagic.com (Postfix) with ESMTP id A6CA53BD2A; Sat, 24 Apr 2004 12:06:28 -0400 (EDT) Message-ID: <408A9093.2050409@mindspring.com> Date: Sat, 24 Apr 2004 12:06:43 -0400 From: Richard Coleman Organization: Critical Magic, Inc. User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Don Lewis References: <200404240540.i3O5eA7E053079@gw.catspoiler.org> In-Reply-To: <200404240540.i3O5eA7E053079@gw.catspoiler.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: kientzle@FreeBSD.org cc: current@FreeBSD.org cc: julian@elischer.org Subject: Re: Testing Tar (was Re: bad news for bsdtar..) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: richardcoleman@mindspring.com List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 24 Apr 2004 16:06:31 -0000 Don Lewis wrote: >>>At least the -current version of tar skips reading the >>>data when it is writing to /dev/null. >> >>A-ha! That explains a few of the odd timings I've seen. >>I wonder why it does that? (Other than to look good on >>benchmarks, of course. ;-) > > > This speeds up Amanda quite a bit. Amanda will run tar with the > --totals option as well as other options to specify either full or > incremental backups multiple times for each file system that it backs > up. It does this to plan the best mixture of full and incremental > backups. If tar actually read the data from disk each time, the > planning phase would take a *lot* longer, and would thrash the disk a > lot more. Until libarchive gets support for sparse files, it's probably better to stick with gtar or rdump with Amanda. But the concept of a version of Amanda that natively uses libarchive is very cool. It seems like a natural target. Richard Coleman richardcoleman@mindspring.com