From: NeilBrown <neilb@suse.de>
To: Ric Wheeler <ricwheeler@gmail.com>
Cc: Chris Friesen <chris.friesen@genband.com>, linux-raid@vger.kernel.org
Subject: Re: RFC: use TRIM data from filesystems to speed up array rebuild?
Date: Wed, 5 Sep 2012 06:24:05 +1000 [thread overview]
Message-ID: <20120905062405.3741239a@notabene.brown> (raw)
In-Reply-To: <5046525E.10500@gmail.com>
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On Tue, 04 Sep 2012 15:11:26 -0400 Ric Wheeler <ricwheeler@gmail.com> wrote:
> On 09/04/2012 02:06 PM, Chris Friesen 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.
> >
> > Thanks,
> > Chris
> >
>
> Device mapper has a "thin" target now that tracks blocks that are allocated or
> free (and works with discard).
>
> That might be a basis for doing an focused RAID rebuild,
I wonder how....
Maybe the block-later interface could grow something equivalent to
"SEEK_HOLE" and friends so that the upper level can find "holes" and
"allocated space" in the underlying device.
I wonder if it is time to discard the 'block device' abstraction and just use
files every .... but I seriously doubt it.
NeilBrown
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next prev parent reply other threads:[~2012-09-04 20:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-04 18:06 RFC: use TRIM data from filesystems to speed up array rebuild? Chris Friesen
2012-09-04 19:11 ` Ric Wheeler
2012-09-04 20:24 ` NeilBrown [this message]
2012-09-04 22:59 ` Ric Wheeler
2012-09-06 17:17 ` Benjamin ESTRABAUD
2012-09-06 18:42 ` David Brown
2012-09-07 9:23 ` Benjamin ESTRABAUD
2012-09-04 20:21 ` NeilBrown
2012-09-04 20:28 ` Chris Friesen
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