Re: RAID5 reconstruction ?

[Redeeman <redeeman@metanurb.dk>]

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.
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html