From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: [PATCH] md: Add support for data integrity to MD Date: Sat, 20 Sep 2008 22:01:29 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: (Dan Williams's message of "Sat\, 20 Sep 2008 17\:26\:40 -0700") Sender: linux-raid-owner@vger.kernel.org To: Dan Williams Cc: "Martin K. Petersen" , jens.axboe@oracle.com, neilb@suse.de, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org List-Id: linux-raid.ids >>>>> "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