From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: thin provisioned LUN support Date: Fri, 7 Nov 2008 12:48:08 -0700 Message-ID: <20081107194807.GI15439@parisc-linux.org> References: <20081107120534.GO21867@kernel.dk> <1226072970.15281.46.camel@think.oraclecorp.com> <1226074002.8030.33.camel@localhost.localdomain> <1226074270.15281.50.camel@think.oraclecorp.com> <1226074710.8030.43.camel@localhost.localdomain> <1226078535.15281.63.camel@think.oraclecorp.com> <4914846C.5060103@redhat.com> <20081107183636.GB29717@mit.edu> <49149A88.4060902@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Tso , Ric Wheeler , Chris Mason , James Bottomley , "Martin K. Petersen" , Jens Axboe , David Woodhouse , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, Black_David@emc.com, Tom Coughlan To: jim owens Return-path: Content-Disposition: inline In-Reply-To: <49149A88.4060902@hp.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Nov 07, 2008 at 02:44:08PM -0500, jim owens wrote: > To do that you kind of have to build a filesystem into the > block layer to persistently store "mapped/unmapped blocks > in chunk" and then do the "unmap-this-chunk" when a region > is all unmapped. > > 250 MB per 1TiB 512b sector disk for a simple 1-bit-per-sector > state. And that assumes you don't replicate it for safety. > That is what the array vendors are trying to avoid by pushing > it off to the OS. And it's what the OS people are trying to avoid having to incorporate by pushing back on the array vendors. > Whoever supports thin provisioning better get their unmapping > correct because those big customers will be looking for who > to blame if they don't get all the features. It's fairly clear that it's the array vendors at fault here. They've designed a shitty product and they're trying to get us to compensate. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."