From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: thin provisioned LUN support Date: Fri, 07 Nov 2008 13:41:35 -0500 Message-ID: <49148BDF.9050707@redhat.com> 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> <20081107183636.GB29717@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.redhat.com ([66.187.237.31]:48216 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbYKGSmK (ORCPT ); Fri, 7 Nov 2008 13:42:10 -0500 In-Reply-To: <20081107183636.GB29717@mit.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Theodore Tso , Ric Wheeler , Chris Mason , James Bottomley "Martin K. Petersen" Theodore Tso wrote: > 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 > T10 is still working on the proposal for how to display unmap related information for SCSI, so we don't even have a consistent way to find this out today for this population. Not sure what is possible for the ATA devices, Ric