From mboxrd@z Thu Jan 1 00:00:00 1970 From: Goswin von Brederlow Subject: Re: RAID5 reconstruction ? Date: Sat, 30 May 2009 20:55:59 +0200 Message-ID: <878wkezagw.fsf@frosties.localdomain> References: <37d33d830905292244w685499b3h391aa2ca7a5b1ad@mail.gmail.com> <4A213612.7080206@anonymous.org.uk> <1243699735.5740.103.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <1243699735.5740.103.camel@localhost> (redeeman@metanurb.dk's message of "Sat, 30 May 2009 18:08:55 +0200") Sender: linux-raid-owner@vger.kernel.org To: Redeeman Cc: John Robinson , SandeepKsinha , Linux RAID List-Id: linux-raid.ids Redeeman writes: > On Sat, 2009-05-30 at 14:35 +0100, John Robinson wrote: >> On 30/05/2009 06:44, SandeepKsinha wrote: >> > Hi all, >> > >> > Say If I have a RAID 5 array of 50GB of five disks of 10GB each. >> > >> > I have data of 5GB. When a disk fails and replaced with a spare disk. >> > Will the reconstruction happen only for the 5GB allocated disk blocks >> > or it will happen for the whole disk size. >> >> The whole disc size, for now anyway; md does not currently note which >> blocks have been used by its client (the filesystem, LVM, whatever). >> >> > Is it possible to make reconstruction intelligent enough to keep it optimized ? >> >> This has been discussed in combination with supporting SSD drives' TRIM >> function, and would mean md had to keep track of used chunks or possibly >> even sectors using a bitmap or something like that, but whether anyone's >> working on it I don't know. > > I would say it should be possible to 'query' the filesystem for that > information. Obviously this will only work if you run a filesystem on it > which supports it, but it would seem like a nicer solution than a bitmap > for it. > >> >> Cheers, >> >> John. And just when I hit send I thought of something else. Instead of the initial sync when creating a raid the bitmap could just mark all blocks as unused. Much faster raid creation. MfG Goswin