From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: mdadm break / restore soft mirror Date: Thu, 13 Dec 2007 12:19:17 +1100 Message-ID: <18272.34965.638276.892803@notabene.brown> References: <05ED21952E28E94E8352836547A6BA37042318B3@achmsx001.hsa.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Brett Maton on Wednesday December 12 Sender: linux-raid-owner@vger.kernel.org To: Brett Maton Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Wednesday December 12, Brett.Maton@simplyhealth.co.uk wrote: > Hi, > > Question for you guys. > > A brief history: > RHEL 4 AS > I have a partition with way to many small files on (Usually around a couple of million) that needs to be backed up, standard > > methods mean that a restore is impossibly slow due to the sheer volume of files. > Solution, raw backup /restore of the device. However the partition is permanently being accessed. > > Proposed solution is to use software raid mirror. Before backup starts, break the soft mirror unmount and backup partition > > restore soft mirror and let it resync / rebuild itself. > > Would the above intentional break/fix of the mirror cause any problems? No, it should work fine. If you can be certain that the device that you break out of the mirror is never altered, then you could add an internal bitmap while the array is split and the rebuild will go much faster. However even mounting a device readonly will sometimes alter the content (e.g. if ext3 needs to replay the journal) so you need to be very careful. NeilBrown