From owner-freebsd-questions@FreeBSD.ORG Wed Mar 31 20:14:14 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EB670106564A for ; Wed, 31 Mar 2010 20:14:14 +0000 (UTC) (envelope-from jmc-freebsd2@milibyte.co.uk) Received: from relay.ptn-ipout02.plus.net (relay.ptn-ipout02.plus.net [212.159.7.36]) by mx1.freebsd.org (Postfix) with ESMTP id 81B618FC1A for ; Wed, 31 Mar 2010 20:14:14 +0000 (UTC) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AlUFACNKs0vUnw4S/2dsb2JhbACPRIt1ccB2hQAE Received: from pih-relay05.plus.net ([212.159.14.18]) by relay.ptn-ipout02.plus.net with ESMTP; 31 Mar 2010 21:14:12 +0100 Received: from [84.92.153.232] (helo=curlew.milibyte.co.uk) by pih-relay05.plus.net with esmtp (Exim) id 1Nx4Im-0005UH-Fz; Wed, 31 Mar 2010 21:14:12 +0100 Received: by curlew.milibyte.co.uk with local (Exim 4.71) (envelope-from ) id 1Nx4Im-0001Pb-6N; Wed, 31 Mar 2010 21:14:12 +0100 From: Mike Clarke To: freebsd-questions@freebsd.org Date: Wed, 31 Mar 2010 21:14:12 +0100 User-Agent: KMail/1.9.10 References: <201003201532.48793.jmc-freebsd2@milibyte.co.uk> <201003311022.44297.jmc-freebsd2@milibyte.co.uk> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201003312114.12156.jmc-freebsd2@milibyte.co.uk> X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: jmc-freebsd2@milibyte.co.uk X-SA-Exim-Scanned: No (on curlew.milibyte.co.uk); SAEximRunCond expanded to false X-Plusnet-Relay: b9c03d441007d871fc9c278ff170076d Cc: krad Subject: Re: Copying mirrored partitions - will this work? 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: Wed, 31 Mar 2010 20:14:15 -0000 On Wednesday 31 March 2010, krad wrote: > On 31 March 2010 10:22, Mike Clarke wrote: > > On Saturday 20 March 2010, Mike Clarke wrote: [snip] > > > I have two 500GB disks, /dev/ad4 and /dev/ad8, each partitioned > > > into 4 slices of 88, 88, 42 and 259GB. My system is installed on > > > the first slices (ad4s1 and ad8s1) which are mirrored as > > > /dev/mirror/gm0. The second slices (ad4s2 and ad8s2) are > > > currently unused. My thoughts are to temporarily add ad4s2 into > > > gm0 with "gmirror insert gm0 ad4s2" and wait for the mirror to > > > synchronise. I should then be able to remove the temporary > > > addition with "gmirror remove gm0 /dev/ad4s2" at which point > > > ad4s2 should be a duplicate of the original system and I can then > > > go ahead and create a new mirror with "gmirror label -b load gm1 > > > ad4s2" and "gmirror insert gm1 ad8s2". After editing /etc/fstab > > > in the new mirror to use gm1 instead of gm0 I should then be able > > > to boot into the system on slice 2 and upgrade it to STABLE while > > > still keeping my original system to fall back to if required. > > > > > > Is this approach of moving disks from one mirror to another > > > workable, or have I missed something that would lead me into deep > > > trouble? I don't mind unduly if I make a mess of the second slice > > > and have to start again but I don't want to lose the contents of > > > my original system on slice 1. > > > > I decided to give it a try and the process went through very > > smoothly. It was much less tedious than bsdlabel -> newfs -> > > dump|restore, and quicker too. The mirror synchronised at a bit > > over 100 MB/sec but dump| restore only gave me about 10 MB/sec. [snip] > One thing about your dump/restore speed. Did you play around with > larger block sizes? Increasing it should give you better throughput. I used 32 MB for the cache size but I expect the reduced speed comes about from the need to find and open a large number of files whereas synchronising the mirror just does a sequential disk to disk copy at block level. -- Mike Clarke