From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756524AbZHZCmJ (ORCPT ); Tue, 25 Aug 2009 22:42:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751081AbZHZCmI (ORCPT ); Tue, 25 Aug 2009 22:42:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47357 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755531AbZHZCmH (ORCPT ); Tue, 25 Aug 2009 22:42:07 -0400 Message-ID: <4A94A0E6.4020401@redhat.com> Date: Tue, 25 Aug 2009 22:41:42 -0400 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Lightning/1.0pre Thunderbird/3.0b3 MIME-Version: 1.0 To: Andrei Tanas CC: "'NeilBrown'" , linux-kernel@vger.kernel.org Subject: Re: MD/RAID: what's wrong with sector 1953519935? References: <004e01ca25e4$c11a54e0$434efea0$@ca> <9cfb6af689a7010df166fdebb1ef516b.squirrel@neil.brown.name> <4A948A82.4080901@redhat.com> <4A94905F.7050705@redhat.com> <005101ca25f4$09006830$1b013890$@ca> In-Reply-To: <005101ca25f4$09006830$1b013890$@ca> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/25/2009 10:22 PM, Andrei Tanas wrote: >>>> One thing that can happen is when we have a hot spot (like the super >>>> block) on high capacity drives is that the frequent write degrade >> the >>>> data in adjacent tracks. Some drives have firmware that watches for >>>> this and rewrites adjacent tracks, but it is also a good idea to >> avoid >>>> too frequent updates. >>> >>> Yet another detail to worry about.... :-( >> >> it never ends :-) >> >>> >>>> >>>> Didn't you have a tunable to decrease this update frequency? >>> >>> /sys/block/mdX/md/safe_mode_delay >>> is a time in seconds (Default 0.200) between when the last write to >>> the array completes and when the superblock is marked as clean. >>> Depending on the actual rate of writes to the array, the superblock >>> can be updated as much as twice in this time (once to mark dirty, >>> once to mark clean). >>> >>> Increasing the number can decrease the update frequency of the >> superblock, >>> but the exact effect on update frequency is very load-dependant. >>> >>> Obviously a write-intent-bitmap, which is rarely more that a few >>> sectors, can also see lots of updates, and it is harder to tune >>> that (you have to set things up when you create the bitmap). >>> >>> NeilBrown >>> >> >> We did see issues in practice with adjacent sectors with some drives, >> so this >> one is worth tuning down. >> >> I would suggest that Andrei might try to write and clear the IO error >> at that >> offset. You can use Mark Lord's hdparm to clear a specific sector or >> just do the >> math (carefully!) and dd over it. It the write succeeds (without >> bumping your >> remapped sectors count) this is a likely match to this problem, > > I've tried dd multiple times, it always succeeds, and the relocated sector > count is currently 1 on this drive, even though this particular fault > happened at least 3 times so far. > I would bump that count way up (say to 2) and see if you have an issue... ric