From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Tso Subject: Re: thin provisioned LUN support Date: Fri, 7 Nov 2008 16:13:47 -0500 Message-ID: <20081107211347.GM29717@mit.edu> References: <1226078535.15281.63.camel@think.oraclecorp.com> <4914846C.5060103@redhat.com> <20081107183636.GB29717@mit.edu> <49148BDF.9050707@redhat.com> <20081107193503.GG29717@mit.edu> <20081107201913.GI29717@mit.edu> <20081107202149.GJ15439@parisc-linux.org> <4914A492.4080009@redhat.com> <1226090910.15281.84.camel@think.oraclecorp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ric Wheeler , Matthew Wilcox , "Martin K. Petersen" , James Bottomley , Jens Axboe , David Woodhouse , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, Black_David@emc.com, Tom Coughlan To: Chris Mason Return-path: Received: from www.church-of-our-saviour.ORG ([69.25.196.31]:38861 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751393AbYKGVN4 (ORCPT ); Fri, 7 Nov 2008 16:13:56 -0500 Content-Disposition: inline In-Reply-To: <1226090910.15281.84.camel@think.oraclecorp.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Nov 07, 2008 at 03:48:30PM -0500, Chris Mason wrote: > > * Fast > * Crash safe > * Bounded ram usage > * Accurately deliver the trims > > Pick any three ;) Actually, if you move this responsibility into the FS block allocator, I think you can get all four. You might pay a slight CPU cost for determining whether the aligned region is free, depending on how the filesystem's block allocation data structures are structured, but the more I think about it, the more I like it. It only has the downside that it would have to be implemented in every filesystem separately, but hey, it's the block array vendors who would be getting the big bucks from having this feature, so they should have no problem putting up some bucks to make sure the OS implements so their users can take advantage of *their* feature. :-) - Ted