Hi Ramazan,
I'm no Ceph expert, but what I can say from my experience using Ceph is:
1) During "Scrubbing", Ceph can be extremely slow. This is probably
where your "blocked requests" are coming from. BTW: Perhaps you can even
find out which processes are currently blocking with: ps aux | grep "D".
You might even want to kill some of those and/or shutdown services in
order to relieve some stress from the machine until it recovers.
2) I usually have the following in my ceph.conf. This lets the scrubbing
only run between midnight and 6 AM (hopefully the time of least demand;
adjust as necessary) - and with the lowest priority.
#Reduce impact of scrub.
osd_disk_thread_ioprio_priority = 7
osd_disk_thread_ioprio_class = "idle"
osd_scrub_end_hour = 6
3) The Scrubbing begin and end hour will always work. The low priority
mode, however, works (AFAIK!) only with CFQ I/O Scheduler. Show your
current scheduler like this (replace sda with your device):
cat /sys/block/sda/queue/scheduler
You can also echo to this file to set a different scheduler.
With these settings you can perhaps alleviate the problem so far, that
the scrubbing runs over many nights until it finished. Again, AFAIK, it
doesnt have to finish in one night. It will continue the next night and
so on.
The Ceph experts say scrubbing is important. Don't know why, but I just
believe them. They've built this complex stuff after all :-)
Thus, you can use "noscrub"/"nodeepscrub" to quickly get a hung server
back to work, but you should not let it run like this forever and a day.
Hope this helps at least a bit.
BR,
Ranjan
Am 22.08.2017 um 15:20 schrieb Ramazan Terzi:
Hello,
I have a Ceph Cluster with specifications below:
3 x Monitor node
6 x Storage Node (6 disk per Storage Node, 6TB SATA Disks, all disks have SSD
journals)
Distributed public and private networks. All NICs are 10Gbit/s
osd pool default size = 3
osd pool default min size = 2
Ceph version is Jewel 10.2.6.
My cluster is active and a lot of virtual machines running on it (Linux and
Windows VM's, database clusters, web servers etc).
During normal use, cluster slowly went into a state of blocked requests.
Blocked requests periodically incrementing. All OSD's seems healthy. Benchmark,
iowait, network tests, all of them succeed.
Yerterday, 08:00:
$ ceph health detail
HEALTH_WARN 3 requests are blocked > 32 sec; 3 osds have slow requests
1 ops are blocked > 134218 sec on osd.31
1 ops are blocked > 134218 sec on osd.3
1 ops are blocked > 8388.61 sec on osd.29
3 osds have slow requests
Todat, 16:05:
$ ceph health detail
HEALTH_WARN 32 requests are blocked > 32 sec; 3 osds have slow requests
1 ops are blocked > 134218 sec on osd.31
1 ops are blocked > 134218 sec on osd.3
16 ops are blocked > 134218 sec on osd.29
11 ops are blocked > 67108.9 sec on osd.29
2 ops are blocked > 16777.2 sec on osd.29
1 ops are blocked > 8388.61 sec on osd.29
3 osds have slow requests
$ ceph pg dump | grep scrub
dumped all in format plain
pg_stat objects mip degr misp unf bytes log disklog state
state_stamp v reported up up_primary acting
acting_primary last_scrub scrub_stamp last_deep_scrub deep_scrub_stamp
20.1e 25183 0 0 0 0 98332537930 3066 3066
active+clean+scrubbing 2017-08-21 04:55:13.354379 6930'23908781
6930:20905696 [29,31,3] 29 [29,31,3] 29 6712'22950171
2017-08-20 04:46:59.208792 6712'22950171 2017-08-20 04:46:59.208792
Active scrub does not finish (about 24 hours). I did not restart any OSD
meanwhile.
I'm thinking set noscrub, noscrub-deep, norebalance, nobackfill, and norecover
flags and restart 3,29,31th OSDs. Is this solve my problem? Or anyone has
suggestion about this problem?
Thanks,
Ramazan
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