From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: split RAID1 during backups? Date: Mon, 24 Oct 2005 09:26:56 -0400 Message-ID: <435CE120.2030003@steeleye.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Jeff Breidenbach Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Jeff Breidenbach wrote: >>However you will endure a rebuild on md0 when you re-add the disk, but >>given everything is mounted read-only, you should not practically be >>doing anything > > > If the rebuild operation is a no-op, then that sounds like a great > idea. If the rebuild operation requires scanning over all data in both > drives, I think that's going to be at least as expensive as the > current 10 hour process. You seem to be using a pretty bleeding edge kernel (2.6.12). If you were to upgrade to 2.6.13, the md bitmap (intent logging) functionality that is present in that kernel will allow the resync to be a no-op. Basically, the bitmap tracks writes to the md array, and then when resync occurs, only syncs blocks that have been written. Since the array would be readonly while you're doing backups, there would be nothing to resync. See the list archives for more details on md bitmap. -- Paul