From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752733AbXGKCvo (ORCPT ); Tue, 10 Jul 2007 22:51:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754692AbXGKCva (ORCPT ); Tue, 10 Jul 2007 22:51:30 -0400 Received: from nz-out-0506.google.com ([64.233.162.238]:54018 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754758AbXGKCv2 (ORCPT ); Tue, 10 Jul 2007 22:51:28 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:x-enigmail-version:content-type:content-transfer-encoding; b=H1Iw5DCZp2tlUiv0MtDwzTXFK4KpeL8uW+zTDBkOpN4b+F9pGVhZAmEmqBjhkMpnIs5c+eMyeUWgwiVpFXYznJfvlC6cqzFmLJO0pNf7tXcR0JlcV6vaMuQmpKrKUlyIHq8ijZZ9Gqhj9JPI7l0cgCkGwzQwaz/6KDJqNNpomsg= Message-ID: <46944555.80509@gmail.com> Date: Wed, 11 Jul 2007 11:49:57 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.4 (X11/20070604) MIME-Version: 1.0 To: Valdis.Kletnieks@vt.edu CC: ric@emc.com, david@lang.hm, Stefan Bader , Phillip Susi , device-mapper development , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Jens Axboe , David Chinner , Andreas Dilger Subject: Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. References: <18006.38689.818186.221707@notabene.brown> <18010.12472.209452.148229@notabene.brown> <20070528094358.GM25091@agk.fab.redhat.com> <5201e28f0705290225v14fdac44hb0382a4137a84d01@mail.gmail.com> <20070529220500.GA6513@agk.fab.redhat.com> <5201e28f0705300212g3be16464u5ee1a4c80db27a11@mail.gmail.com> <465DAC72.1010201@cfl.rr.com> <5201e28f0705310414u1a9aebc4je135748274543946@mail.gmail.com> <465F9197.7060002@gmail.com> <465FC7B1.3060309@gmail.com> <4693D26D.2060004@emc.com> <4758.1184110800@turing-police.cc.vt.edu> In-Reply-To: <4758.1184110800@turing-police.cc.vt.edu> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Valdis.Kletnieks@vt.edu wrote: > On Tue, 10 Jul 2007 14:39:41 EDT, Ric Wheeler said: > >> All of the high end arrays have non-volatile cache (read, on power loss, it is a >> promise that it will get all of your data out to permanent storage). You don't >> need to ask this kind of array to drain the cache. In fact, it might just ignore >> you if you send it that kind of request ;-) > > OK, I'll bite - how does the kernel know whether the other end of that > fiberchannel cable is attached to a DMX-3 or to some no-name product that > may not have the same assurances? Is there a "I'm a high-end array" bit > in the sense data that I'm unaware of? Well, the array just has to tell the kernel that it doesn't to write back caching. The kernel automatically selects ORDERED_DRAIN in such case. -- tejun