On Sun, May 31, 2009 at 1:07 AM, Redeeman <redeeman@xxxxxxxxxxx> wrote: > On Sat, 2009-05-30 at 20:55 +0200, Goswin von Brederlow wrote: >> Redeeman <redeeman@xxxxxxxxxxx> 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. > 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. 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 suppose > in worst case, mounted... > >> >> MfG >> Goswin >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- Regards, Sandeep. “To learn is to change. Education is a process that changes the learner.” -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
