From mboxrd@z Thu Jan 1 00:00:00 1970 From: Redeeman Subject: Re: Poor write performance with write-intent bitmap? Date: Sat, 23 May 2009 01:00:25 +0200 Message-ID: <1243033225.5740.30.camel@localhost> References: <49ED096E.1000002@anonymous.org.uk> <49ED16F7.3040906@anonymous.org.uk> <4081b80da35818efbc07723240f8ea36.squirrel@neil.brown.name> <49ED2BC3.7050109@anonymous.org.uk> <18925.24241.19288.797776@notabene.brown> <49EDB685.7000004@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49EDB685.7000004@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: John Robinson Cc: Linux RAID List-Id: linux-raid.ids On Tue, 2009-04-21 at 13:05 +0100, John Robinson wrote: > On 21/04/2009 06:50, Neil Brown wrote: > > On Tuesday April 21, john.robinson@anonymous.org.uk wrote: > >> Eeek! Trying to `mdadm --grow /dev/md1 --bitmap=none` from my large > >> chunk size caused a reboot! There's nothing in the log, and I didn't see > >> the console. I still have my 32M chunksize but I don't want to try that > >> again in a hurry :-) > > > > That's a worry... I cannot easily reproduce it. If it happens again > > and you get any more detail, I'm sure you'll let me know. > > Sure will. For the moment I have something that looks slightly > inconsistent: mdadm --detail shows no bitmap after the crash: > # mdadm --detail /dev/md1 > /dev/md1: > Version : 00.90.03 > Creation Time : Mon Jul 28 15:49:09 2008 > Raid Level : raid5 > Array Size : 1953310720 (1862.82 GiB 2000.19 GB) > Used Dev Size : 976655360 (931.41 GiB 1000.10 GB) > Raid Devices : 3 > Total Devices : 3 > Preferred Minor : 1 > Persistence : Superblock is persistent > > Update Time : Tue Apr 21 12:37:15 2009 > State : clean > Active Devices : 3 > Working Devices : 3 > Failed Devices : 0 > Spare Devices : 0 > > Layout : left-symmetric > Chunk Size : 256K > > UUID : d8c57a89:166ee722:23adec48:1574b5fc > Events : 0.6152 > > Number Major Minor RaidDevice State > 0 8 2 0 active sync /dev/sda2 > 1 8 18 1 active sync /dev/sdb2 > 2 8 34 2 active sync /dev/sdc2 > > and indeed another attempt to remove the bitmap fails gently: > # mdadm --grow /dev/md1 --bitmap none > mdadm: no bitmap found on /dev/md1 > > However examining any of the devices making up the RAID appears to > suggest there is a bitmap: > # mdadm --examine-bitmap /dev/sda2 > Filename : /dev/sda2 > Magic : 6d746962 > Version : 4 > UUID : d8c57a89:166ee722:23adec48:1574b5fc > Events : 6148 > Events Cleared : 6148 > State : OK > Chunksize : 32 MB > Daemon : 5s flush period > Write Mode : Normal > Sync Size : 976655360 (931.41 GiB 1000.10 GB) > Bitmap : 29806 bits (chunks), 10 dirty (0.0%) > > Is this to be expected? I would have thought it would say nothing here, > or say there's no bitmap. Hmm very good question, I'd like to know that aswell.. > Many thanks for all your advice and assistance. > > Cheers, > > John. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html