From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Gr=E9goire_Pichon?= Subject: IO errors when tuning max_sectors_kb value of a dm device Date: Mon, 04 Apr 2011 18:24:11 +0200 Message-ID: <4D99F0AB.90406@bull.net> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids Hi all, If dm-devel is the good list to ask questions, could anyone have a look at my problem ? I observe some IO errors on a multipath device for which the max_sectors_kb parameter has been tunned. Value is increased from the default (1024) to the value of the hw max sectors (32768). The following error appears in the system log: 1301326968 2011 Mar 28 17:42:48 berlin4 kern err kernel blk_rq_check_limits: over max size limit. Followed by several I/O errors 1301326968 2011 Mar 28 17:42:48 berlin4 kern err kernel end_request: I/O error, dev dm-10, sector 26624 1301326968 2011 Mar 28 17:42:48 berlin4 kern err kernel end_request: I/O error, dev dm-10, sector 24576 1301326968 2011 Mar 28 17:42:48 berlin4 kern err kernel end_request: I/O error, dev dm-10, sector 22528 ... I have seen in the device-mapper source code that when a multipath device is configured, its limits are computed from a combination of all the slave devices it uses (dm_calculate_queue_limits()). Does it mean that tuning the dm device is forbidden ? Is there way to re-validate the queue limits after the tuning ? Do you think it would be safe if I additionally tune the max_sectors_kb parameter of the slave devices ? Thanks in advance, Gregoire.