From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263573AbTJ0V3I (ORCPT ); Mon, 27 Oct 2003 16:29:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263575AbTJ0V3I (ORCPT ); Mon, 27 Oct 2003 16:29:08 -0500 Received: from mail-in-03.arcor-online.net ([151.189.21.43]:52655 "EHLO mail-in-03.arcor-online.net") by vger.kernel.org with ESMTP id S263573AbTJ0V3G (ORCPT ); Mon, 27 Oct 2003 16:29:06 -0500 From: Daniel Phillips To: Lars Marowsky-Bree , Nick Piggin Subject: Re: [PATCH] ide write barrier support Date: Mon, 27 Oct 2003 23:35:17 +0200 User-Agent: KMail/1.5.3 Cc: Jens Axboe , Linux Kernel References: <20031013140858.GU1107@suse.de> <200310262206.53904.phillips@arcor.de> <20031027102919.GC13640@marowsky-bree.de> In-Reply-To: <20031027102919.GC13640@marowsky-bree.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200310272235.17845.phillips@arcor.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 27 October 2003 11:29, Lars Marowsky-Bree wrote: > On 2003-10-26T23:06:53, > > Daniel Phillips said: > > Not entirely within the multipath virtual device, that's the problem. > > If it could stay somehow all within one device driver then ok, but > > since we want to build this modularly, as a device mapper target, > > there are API issues. > > Are you seeing problems with the write-ordering properties of > multipathing? If so, what is the issue with handling them in the DM > target once? No, no problem. A multipath write barrier can be handled by blocking incoming writes in the target and waiting for all outstanding writes to complete. I'd prefer to let the write barrier flow down the pipe to the SCSI disk if I could, but there are technical challenges. Mainly I need to know if an ordered write is able to read its buffer into the drive's cache while it is waiting for preceding commands to complete; if so it would be worth putting the effort into developing the flow-through scheme. Regards, Daneil