From mboxrd@z Thu Jan 1 00:00:00 1970 From: Goswin von Brederlow Subject: Re: RAID5 reconstruction ? Date: Sun, 31 May 2009 13:54:29 +0200 Message-ID: <87ljod7aiy.fsf@frosties.localdomain> References: <37d33d830905292244w685499b3h391aa2ca7a5b1ad@mail.gmail.com> <4A213612.7080206@anonymous.org.uk> <1243699735.5740.103.camel@localhost> <878wkezagw.fsf@frosties.localdomain> <1243712247.5740.105.camel@localhost> <37d33d830905310102m451f26aaw8e233227cda491c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <37d33d830905310102m451f26aaw8e233227cda491c@mail.gmail.com> (sandeepksinha@gmail.com's message of "Sun, 31 May 2009 13:32:03 +0530") Sender: linux-raid-owner@vger.kernel.org To: SandeepKsinha Cc: Redeeman , Goswin von Brederlow , John Robinson , Linux RAID List-Id: linux-raid.ids SandeepKsinha writes: > On Sun, May 31, 2009 at 1:07 AM, Redeeman wrot= e: >> On Sat, 2009-05-30 at 20:55 +0200, Goswin von Brederlow wrote: >>> And just when I hit send I thought of something else. >>> >>> Instead of the initial sync when creating a raid the bitmap could j= ust >>> mark all blocks as unused. Much faster raid creation. >> > > > This really sounds like a good option. This would have a slight hit > for writes which I believe will compensate for later re-constructions= , > replacing a disk, mirror resysnc and many more operation. What hit? Currently with bitmap support a write will set the block to "unclean", write the data, write the parity and set the block to "clean". Setting the "used" bit along the way should not cost much. Only difference I see is that the bitmap would have to have finer granularity so one "used" bit covers one filesystem block (4k usualy). Otherwise you could only "use" blocks but not "unuse" them again when the filesystem frees them in 4k chunks. > Neil any comments on this? > > I mean, how difficult would it be to maintain such a bitmap. This can > though of making something optional as this will incur space. > > >> A filesystem-coexist mode could also do this, by simply refusing >> operation until such a time that a filesystem is detected, or i supp= ose >> in worst case, mounted... > > >> >>> >>> MfG >>> =A0 =A0 =A0 =A0 Goswin MfG Goswin -- 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