From mboxrd@z Thu Jan 1 00:00:00 1970 From: maurice Subject: Re: Rotating RAID 1 Date: Mon, 15 Aug 2011 22:36:18 -0600 Message-ID: <4E49F3C2.8090009@gmail.com> References: <4E497FB5.3030109@ivitera.com> <4E49849E.4030604@ivitera.com> <20110816084251.2d8e7831@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110816084251.2d8e7831@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: Pavel Hofman , =?ISO-8859-1?Q?J=E9r=F4me_?= =?ISO-8859-1?Q?Poulin?= , linux-raid List-Id: linux-raid.ids On 8/15/2011 4:42 PM, NeilBrown wrote: > ..I'm not sure from you description whether the following describes > exactly > what you are doing or not, but this is how I would do it. > As you say, you need two bitmaps. > So if there are 3 drives A, X, Y where A is permanent and X and Y are > rotated off-site, > then I create two RAID1s like this: > mdadm -C /dev/md0 -l1 -n2 --bitmap=internal /dev/A /dev/X > mdadm -C /dev/md1 -l1 -n2 --bitmap=internal /dev/md0 /dev/Y > > mkfs /dev/md1; mount /dev/md1 ... > > Then you can remove either or both of X and Y and which each is > re-added it will > recover just the blocks that it needs. > X from the bitmap of md0, Y from the bitmap of md1. > > NeilBrown How elegantly described. After so many instances of being told "You should not use RAID as a backup device like that!" it is pleasant to hear you detail the "right way" to do this. Thank you very much for that Neil. -- Cheers, Maurice Hilarius eMail: /mhilarius@gmail.com/