From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin ESTRABAUD Subject: MD: "sync_action" issues: pausing resync/recovery automatically restarts. Date: Thu, 11 Feb 2010 12:02:56 +0000 Message-ID: <4B73F1F0.1030800@mpstor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi everybody, I am getting a weird issue when I am writing values to "/sys/block/mdX/md/sync_action". For instance, I would like to pause a resync or/and a recovery when they are happening. I create a RAID 5 as follow: mdadm --create -vvv --force --run --metadata=1.2 /dev/md/d0 --level=5 --size=9429760 --chunk=64 --name=1056856 -n5 --bitmap=internal --bitmap-chunk=4096 --layout=ls /dev/sde2 /dev/sdb2 /dev/sdc2 /dev/sdf2 /dev/sdd2 The RAID is resyncing: # cat /proc/mdstat Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] md_d0 : active raid5 sdd2[4] sdf2[3] sdc2[2] sdb2[1] sde2[0] 37719040 blocks super 1.2 level 5, 64k chunk, algorithm 2 [5/5] [UUUUU] [====>................] resync = 22.2% (2101824/9429760) finish=2.6min speed=46186K/sec bitmap: 1/1 pages [64KB], 4096KB chunk unused devices: I then decide to pause its resync: # echo idle > /sys/block/md_d0/md/sync_action The RAID resync should have paused by now, let's check the sys properties: # cat /sys/block/md_d0/md/sync_action resync The resync seems to have not stopped/restarted, let's check dmesg: [157287.049715] raid5: raid level 5 set md_d0 active with 5 out of 5 devices, algorithm 2 [157287.057601] RAID5 conf printout: [157287.060909] --- rd:5 wd:5 [157287.063700] disk 0, o:1, dev:sde2 [157287.067182] disk 1, o:1, dev:sdb2 [157287.070664] disk 2, o:1, dev:sdc2 [157287.074147] disk 3, o:1, dev:sdf2 [157287.077628] disk 4, o:1, dev:sdd2 [157287.086813] md_d0: bitmap initialized from disk: read 1/1 pages, set 2303 bits [157287.094134] created bitmap (1 pages) for device md_d0 [157287.113475] md: resync of RAID array md_d0 [157287.117650] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [157287.123555] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync. [157287.133011] md: using 2048k window, over a total of 9429760 blocks. [157345.158535] md: md_do_sync() got signal ... exiting [157345.166057] md: checkpointing resync of md_d0. [157345.179819] md: resync of RAID array md_d0 [157345.183993] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [157345.189899] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync. [157345.199353] md: using 2048k window, over a total of 9429760 blocks. The resync seem to stop at some stage since: [157345.158535] md: md_do_sync() got signal ... exiting But it seems to be restarting right after this: [157345.179819] md: resync of RAID array md_d0 I read in the md.txt documentation that pausing a resync could sometimes not work if a n event or trigger was triggering it to automatically restart. However, I don't think I have any trigger that would cause it to restart. it then builds perfectly fine. I now want to check if the same issue occurs while recovering, after all, I especially want to be able to pause a recovery, while I don't really need to pause/restart resyncs. Let's say I pull a disk from the bay, fail it and remove it as follow: # mdadm --fail /dev/md/d0 /dev/sde2 mdadm: set /dev/sde2 faulty in /dev/md/d0 # mdadm --remove /dev/md/d0 /dev/sde2 mdadm: hot removed /dev/sde2 Now let's add a spare: # /opt/soma/bin/mdadm/mdadm --add /dev/md/d0 /dev/sda2 raid manager: added /dev/sda2 The RAID is now recovering: # cat /proc/mdstat Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] md_d0 : active raid5 sda2[5] sdd2[4] sdf2[3] sdc2[2] sdb2[1] 37719040 blocks super 1.2 level 5, 64k chunk, algorithm 2 [5/4] [_UUUU] [>....................] recovery = 1.7% (169792/9429760) finish=0.9min speed=169792K/sec bitmap: 0/1 pages [0KB], 4096KB chunk unused devices: # cat /sys/block/md_d0/md/sync_action recover Let's try and stop this recovery: # echo idle > /sys/block/md_d0/md/sync_action [157641.618291] disk 3, o:1, dev:sdf2 [157641.621774] disk 4, o:1, dev:sdd2 [157641.632057] md: recovery of RAID array md_d0 [157641.636413] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [157641.642314] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for recovery. [157641.651940] md: using 2048k window, over a total of 9429760 blocks. [157657.120722] md: md_do_sync() got signal ... exiting [157657.267055] RAID5 conf printout: [157657.270381] --- rd:5 wd:4 [157657.273171] disk 0, o:1, dev:sda2 [157657.276650] disk 1, o:1, dev:sdb2 [157657.280129] disk 2, o:1, dev:sdc2 [157657.283605] disk 3, o:1, dev:sdf2 [157657.287087] disk 4, o:1, dev:sdd2 [157657.290568] RAID5 conf printout: [157657.293876] --- rd:5 wd:4 [157657.296660] disk 0, o:1, dev:sda2 [157657.300139] disk 1, o:1, dev:sdb2 [157657.303615] disk 2, o:1, dev:sdc2 [157657.307096] disk 3, o:1, dev:sdf2 [157657.310579] disk 4, o:1, dev:sdd2 [157657.320835] md: recovery of RAID array md_d0 [157657.325194] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [157657.331091] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for recovery. [157657.340713] md: using 2048k window, over a total of 9429760 blocks. [157657.347047] md: resuming recovery of md_d0 from checkpoint. I am getting the same issue, the recovery stops, but restarts 200 milliseconds later. This clearly indicates that some sort of trigger is automatically restarting the resync and recovery, but I have no clue as of what could it be. Would anyone here had a similar experience with trying to stop resyncs? Is there a "magic" variable that would enable or disable automatic restart of resync/recoveries? Would anyone know of a standard event or trigger that would cause a resync or recovery to automatically restart? Thank you very much in advance for your help. My Kernel version is: 2.6.26.3 Ben.