From mboxrd@z Thu Jan 1 00:00:00 1970 From: Herta Van den Eynde Subject: Re: what happens to raid when more disks are added? Date: Thu, 08 May 2003 10:10:34 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <3EBA10FA.2020004@cc.kuleuven.ac.be> References: <3EB929C3.6040400@cc.kuleuven.ac.be> <3EB93643.D55A2AD5@SteelEye.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: Paul Clements Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Paul Clements wrote: >Herta Van den Eynde wrote: > > > >>To linux, they are known as devices sd[c-h], which have been configured >>as raid 0+1: >> >># cat /proc/mdstat >>Personalities : [raid0] [raid1] >>read_ahead 1024 sectors >>md2 : active raid1 md1[1] md0[0] >> 106679168 blocks [2/2] [UU] >> >>md0 : active raid0 sde1[2] sdd1[1] sdc1[0] >> 106679232 blocks 8k chunks >> >>md1 : active raid0 sdh1[2] sdg1[1] sdf1[0] >> 106679232 blocks 8k chunks >> >>unused devices: >> >> > >It's generally thought to be better to set this up as a RAID 1+0 (three >raid1 devices striped together) but maybe there's a reason why you've >opted for the RAID 0+1? (there's one less md device, I guess)... > > > > >>When I need to add extra disks, e.g. in slots 3 and 12, I assume that >>the disk in slot 3 will get device name /dev/sdf, and the disks in slots >>9 through 12 will subsequently be known as /dev/sd[g-j]. How will that >>affect the raid 0+1 config? >> >> > >You may want to think about using the autodetection feature of md (or >mdadm's UUID capability)... these would allow you to avoid messing >things up if your drive letters shift on you... > >-- >Paul > > Thanks, Paul. Raid 1+0 definitely was and is on my wish list, but when I set up the initial systems, I had no time to play around and check things out. I was nervous about the potential impact of devices changing names, and figured that it'd be easier to manage with a raid 0+1, as it'd be easy to break the mirror and take it from there. I've got a bit more time now, so I'll check out autodetection and uuid. Kind regards, Herta -- ****************************************************** Herta Van den Eynde Toledo system management K.U.Leuven - Ludit W.de Croylaan 52A B-3001 Heverlee Belgium tel: +32 (0)16 322 166 fax: +32 (0)16 322 999 ****************************************************** "For something fulfilled this hour, loved or endured." (W.H. Auden) ******************************************************