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: <none>
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: <none>
# 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.
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