Re: RFC: use TRIM data from filesystems to speed up array rebuild?

[Chris Friesen <chris.friesen@xxxxxxxxxxx>]

On 09/04/2012 02:21 PM, NeilBrown wrote:
> On Tue, 04 Sep 2012 12:06:26 -0600 Chris Friesen<chris.friesen@xxxxxxxxxxx>
> wrote:
> > Hi,
> >
> > I'm not really a filesystem guy so this may be a really dumb question.
> >
> > We currently have an issue where we have a ~1TB RAID1 array that is
> > mostly given over to LVM.  If we swap one of the disks it will rebuild
> > everything, even though we may only be using a small fraction of the space.
> >
> > This got me thinking.  Has anyone given thought to using the TRIM
> > information from filesystems to allow the RAID code to maintain a
> > bitmask of used disk blocks and only sync the ones that are actually used?
> >
> > Presumably this bitmask would itself need to be stored on the disk.
> Something like this?
>    http://neil.brown.name/blog/20110216044002#5

Something like that would indeed cover the use-case that triggered this.

Chris
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