From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753316AbYIUCBs (ORCPT ); Sat, 20 Sep 2008 22:01:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752407AbYIUCBj (ORCPT ); Sat, 20 Sep 2008 22:01:39 -0400 Received: from rgminet01.oracle.com ([148.87.113.118]:39364 "EHLO rgminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751259AbYIUCBi (ORCPT ); Sat, 20 Sep 2008 22:01:38 -0400 To: "Dan Williams" Cc: "Martin K. Petersen" , jens.axboe@oracle.com, neilb@suse.de, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: [PATCH] md: Add support for data integrity to MD From: "Martin K. Petersen" Organization: Oracle References: Date: Sat, 20 Sep 2008 22:01:29 -0400 In-Reply-To: (Dan Williams's message of "Sat\, 20 Sep 2008 17\:26\:40 -0700") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Brightmail-Tracker: AAAAAQAAAAI= X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Dan" == Dan Williams writes: >> + /* Data integrity passthrough not supported on RAID 4, 5 and 6 */ >> + if (pers->level >= 4 && pers->level <= 6) + return 0; Dan> Do you have a reference to the issues in supporting this? Not really. The protection information is an extra 8-bytes of stuff per sector. But it comes down in a different buffer. To do R-M-W effectively we'll have to maintain a separate protection information stripe cache. And we'll have to generate DIF checksums and reference tags for the parity sectors going out. Quite frankly it's a lot of ick and I haven't completely wrapped my head around it yet. -- Martin K. Petersen Oracle Linux Engineering