Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754997Ab3CWDsJ (ORCPT ); Fri, 22 Mar 2013 23:48:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750994Ab3CWDsH (ORCPT ); Fri, 22 Mar 2013 23:48:07 -0400 Date: Sat, 23 Mar 2013 03:48:03 +0000 From: Alasdair G Kergon To: Mike Snitzer , "Darrick J. Wong" Cc: Heinz Mauelshagen , linux-kernel@vger.kernel.org, device-mapper development , Mikulas Patocka , Linus Torvalds , Joe Thornber Subject: Re: [dm-devel] dm: dm-cache fails to write the cache device in writethrough mode Message-ID: <20130323034803.GB30269@agk-dp.fab.redhat.com> Mail-Followup-To: Mike Snitzer , "Darrick J. Wong" , Heinz Mauelshagen , linux-kernel@vger.kernel.org, device-mapper development , Mikulas Patocka , Linus Torvalds , Joe Thornber References: <20130322201151.GB5357@blackbox.djwong.org> <20130322223425.GA5638@redhat.com> <20130322231600.GD5357@blackbox.djwong.org> <20130323032715.GA7692@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130323032715.GA7692@redhat.com> Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: 64 Baker Street, 4th floor, London, W1U 7DF. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 735 Lines: 19 On Fri, Mar 22, 2013 at 11:27:16PM -0400, Mike Snitzer wrote: > So the big difference is the thinp-test-suite uses intermediate linear > DM layers above the slower sd device (spindle/data) -- whereas in your > setup the origin device is direct to sd (8:0). I would think the difference is because DM issues (edited) copies of incoming bios to the layers underneath, so changes don't propagate back up. Darrick: if you retest with a dm linear device, does the problem go away? Alasdair -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/