From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Boissonneault Subject: Re: RAID5 reconstruction ? Date: Sat, 30 May 2009 10:06:35 -0400 Message-ID: <4A213D6B.8040501@usherbrooke.ca> References: <37d33d830905292244w685499b3h391aa2ca7a5b1ad@mail.gmail.com> <4A213612.7080206@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4A213612.7080206@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: John Robinson Cc: SandeepKsinha , Linux RAID List-Id: linux-raid.ids John Robinson a =E9crit : > 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= =2E >> Will the reconstruction happen only for the 5GB allocated disk block= s >> or it will happen for the whole disk size. > > The whole disc size, for now anyway; md does not currently note which= =20 > blocks have been used by its client (the filesystem, LVM, whatever). > >> Is it possible to make reconstruction intelligent enough to keep it= =20 >> optimized ? > > This has been discussed in combination with supporting SSD drives'=20 > TRIM function, and would mean md had to keep track of used chunks or=20 > possibly even sectors using a bitmap or something like that, but=20 > whether anyone's working on it I don't know. > I don't know how it goes for Linux, but hasn't ZFS been developped=20 exactly for that purpose ? From what I understand, ZFS manage both the=20 file system and the RAID features at once. Therefore, the "raid" part=20 knows where are the files and the filesystem knows about the raid.=20 Reconstruction is then done intelligently (not reconstructing unused sp= ace). Maxime Boissonneault -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html