From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Rabbitson Subject: Re: component growing in raid5 Date: Mon, 24 Mar 2008 16:42:17 +0100 Message-ID: <47E7CBD9.4020900@rabbit.us> References: <47E5FFB8.5030903@bteam.hu> <47E753C4.7030903@rabbit.us> <47E7C609.9000501@bteam.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47E7C609.9000501@bteam.hu> Sender: linux-raid-owner@vger.kernel.org To: Nagy Zoltan Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Nagy Zoltan wrote: > hi > >> I would simply use a v1.1 superblock which will be situated at the >> start of >> the array. Then you will face another problem - once you grow a leaf >> device, >> mdadm will not see the new size as it will find the superblock at sect >> 0 and >> will be done there. You will need to issue mdadm -A ... --update >> devicesize. >> The rest of the operations are identical. > i feeled that there is another solution that i missed - thank you, next > time > i will do it this way -- because the system is already up and running, i > don't wan't > to recreate the array (about the chunksize: i've got back to 64Kb chunks > because > of that bug - i was happy to see it running ;) >> >> As a side note I am also curious why do you go the raid55 path (I am >> not very >> impressed however :) > okay - i've run thru the whole scenario a few times - and always come > get back > to raid55, what would you do in myplace? :) The validity of the snipped arguments depends on how many devices you have at every level: *) how many nodes there are? *) how many disks per node? do all nodes have an equal amount of disks? Without additional info I would say this: The problem with using raid5 on the top node is that you are stressing your network additionally for every r-m-w-cycle. Also rebuild of this array, especially if you add more leaves will be more and more resource intensive. In contrast if the top array is RAID10 with 2 chunk copies, you will sacrifice half the space, however your rebuild will utilize only 2 drives (one reader one writer). HTH Peter