From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: RFC: use TRIM data from filesystems to speed up array rebuild? Date: Tue, 04 Sep 2012 15:11:26 -0400 Message-ID: <5046525E.10500@gmail.com> References: <50464322.3010509@genband.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50464322.3010509@genband.com> Sender: linux-raid-owner@vger.kernel.org To: Chris Friesen Cc: Neil Brown , linux-raid@vger.kernel.org List-Id: linux-raid.ids 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, Ric