From owner-freebsd-questions@FreeBSD.ORG Tue Nov 1 21:15:47 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org 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 21F0616A41F for ; Tue, 1 Nov 2005 21:15:47 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id A2BDE43D45 for ; Tue, 1 Nov 2005 21:15:46 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 17DF25DF1; Tue, 1 Nov 2005 16:15:46 -0500 (EST) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 51278-07; Tue, 1 Nov 2005 16:15:45 -0500 (EST) Received: from [192.168.1.3] (pool-68-161-122-227.ny325.east.verizon.net [68.161.122.227]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id E5F5B5DAE; Tue, 1 Nov 2005 16:15:44 -0500 (EST) Message-ID: <4367DB06.5030400@mac.com> Date: Tue, 01 Nov 2005 16:15:50 -0500 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 X-Accept-Language: en-us, en MIME-Version: 1.0 To: user References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: freebsd-questions@freebsd.org Subject: Re: two quick conceptual questions RE: rsync (and rsyncing snapshots) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Nov 2005 21:15:47 -0000 user wrote: > First, how does rsync respond to, and perform, when the source filesystem > is under very heavy change ? If I have a filesystem that I want to rsync > up to a backup server, but that filesystem is _very busy_ with the > creation, destruction and changing of files, how well does rsync perform, > and how much does it interfere with the performance of the underlying > filesystem that it is sending up to the backup server ? rsync complains when the filesystem changes underneath it, but it will continue to run. On the other hand, rsync is not going to safely maintain the referential integrity of a complex file like a live database, but it's okay for most other things including mbox's. Rsync imposes a significant workload if you are syncronizing a large tree of stuff which changes a lot, but it's efficient considering the size of the task. > Related: it occurs to me that perhaps it would be better to snapshot the > filesystem, mount the snapshot, and then rsync the snapshot. On the other > hand, the filesystem is continuously altering the snapshot as files are > destroyed or changed ... so perhaps this does not gain anything. Is > rsyncing a snapshot of a busy filesystem always, ever or never easier than > rsyncing the busy filesystem itself ? rsync'ing a snapshot is a fine idea. > Finally, am I correct that there are _only two_ rsync comparison methods - > the default checksum method, and the --size-only method ? Am I correct > that rsync _always_ looks at the timestamp first, and then applies either > checksum or size comparison ONLY IF the timestamps are different ? No, rsync checks both timestamp and size or checksum. -- -Chuck