From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Tso Subject: Re: thin provisioned LUN support Date: Fri, 7 Nov 2008 13:36:36 -0500 Message-ID: <20081107183636.GB29717@mit.edu> References: <1225984628.4703.80.camel@localhost.localdomain> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from www.church-of-our-saviour.ORG ([69.25.196.31]:42851 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750978AbYKGSgm (ORCPT ); Fri, 7 Nov 2008 13:36:42 -0500 Content-Disposition: inline In-Reply-To: <4914846C.5060103@redhat.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Ric Wheeler Cc: 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 , Matthew Wilcox On Fri, Nov 07, 2008 at 01:09:48PM -0500, Ric Wheeler wrote: > > I don't think that trim bugs should be that common - we just have to be > very careful never to send down a trim for any uncommitted block. > The trim code probably deserves a very aggressive unit test to make sure it works correctly, but yeah, we should be able to control any trim bugs. > Simple is always good, but I still think that the coalescing (even basic > coalescing) will be a critical performance feature. Will we be able to query the device and find out its TRIM/UNMAP alignment requirements? There is also a balanace between performance (at least if the concern is sending too many separate TRIM commands) and giving the SSD more flexibility in its wear-leveling allocation decisions by sending TRIM commands sooner rather than later. - Ted