From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: thin provisioned LUN support Date: Fri, 7 Nov 2008 13:21:49 -0700 Message-ID: <20081107202149.GJ15439@parisc-linux.org> References: <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> <49148BDF.9050707@redhat.com> <20081107193503.GG29717@mit.edu> <20081107201913.GI29717@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from palinux.external.hp.com ([192.25.206.14]:35124 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbYKGUVv (ORCPT ); Fri, 7 Nov 2008 15:21:51 -0500 Content-Disposition: inline In-Reply-To: <20081107201913.GI29717@mit.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Theodore Tso , "Martin K. Petersen" , Ric Wheeler , Chris Mason , James Bottomley On Fri, Nov 07, 2008 at 03:19:13PM -0500, Theodore Tso wrote: > Let's be just a *little* bit fair here. Suppose we wanted to > implement thin-provisioned disks using devicemapper and LVM; consider > that LVM uses a default PE size of 4M for some very good reasons. > Asking filesystems to be a little smarter about allocation policies so > that we allocate in existing 4M chunks before going onto the next, and > asking the block layer to pool trim requests to 4M chunks is not > totally unreasonable. > > Array vendors use chunk sizes > than typical filesystem chunk sizes > for the same reason that LVM does. So to say that this is due to > purely a "broken firmware architecture" is a little unfair. I think we would have a full-throated discussion about whether the right thing to do was to put the tracking in the block layer or in LVM. Rather similar to what we're doing now, in fact. -- 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."