From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: thin provisioned LUN support Date: Fri, 07 Nov 2008 07:14:58 -0500 Message-ID: <49143142.4010809@redhat.com> References: <4913028B.6010405@redhat.com> <1225984628.4703.80.camel@localhost.localdomain> <20081107120534.GO21867@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: David Woodhouse , James Bottomley , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, Black_David@emc.com, "Martin K. Petersen" , Tom Coughlan , Matthew Wilcox To: Jens Axboe Return-path: In-Reply-To: <20081107120534.GO21867@kernel.dk> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Jens Axboe wrote: > On Thu, Nov 06 2008, David Woodhouse wrote: > >> On Thu, 6 Nov 2008, James Bottomley wrote: >> >>> The way to do this properly would be to run a chequerboard of partials, >>> but this would effectively have trim region tracking done in the block >>> layer ... is this worth it? >>> >>> By the way, the latest (from 2 days ago) version of the Thin >>> Provisioning proposal is here: >>> >>> http://www.t10.org/ftp/t10/document.08/08-149r4.pdf >>> >>> I skimmed it but don't see any update implying that trim might be >>> ineffective if we align wrongly ... where is this? >>> >> I think we should be content to declare such devices 'broken'. >> >> They have to keep track of individual sectors _anyway_, and dropping >> information for small discard requests is just careless. >> > > I agree, seems pretty pointless. Lets let evolution take care of this > issue. I have to say I'm surprised that it really IS an issue to begin > with, are array firmwares really that silly? > > It's not that it would be hard to support (and it would eliminate the > need to do discard merging in the block layer), but it seems like one of > those things that will be of little use in even in the near future. > Discard merging should be useful, I have no problem merging something > like that. > > I think that discard merging would be helpful (especially for devices with more reasonable sized unmap chunks). Ric