Hi
Thanks, we were able to resolve the problem by disabling swap completely, no
need for it anyway.
Also memory was fragmenting since all memory was used for caching
Running “perf top” we saw that freeing blocks of memory took all the cpu power
Samples: 4M of event 'cycles', Event count (approx.): 965471653281
71.95% [kernel] [k] isolate_freepages_block
10.37% [kernel] [k] __reset_isolation_suitable
Now by forcing systems to have 10GB of free memory all the time, the problem
was solved.
We added
vm.min_free_kbytes = 10000000
to /etc/sysctl.conf
Don’t know why this happens, is this a “problem” of the kernel version we are
running or something else. (Ubuntu 14.04 3.13.0-32-generic)
Br,
Tuomas
From: Константин Сахинов [mailto:[email protected]]
Sent: 7. elokuuta 2015 21:15
To: Tuomas Juntunen; Quentin Hartman
Cc: ceph-users
Subject: Re: [ceph-users] Flapping OSD's when scrubbing
Hi!
One time I faced such a behavior of my home cluster. At the time my OSDs go
down I noticed that node is using swap despite of sufficient memory. Tuning
/proc/sys/vm/swappiness to 0 helped to solve the problem.
пт, 7 авг. 2015 г. в 20:41, Tuomas Juntunen <[email protected]>:
Thanks
We play with the values a bit and see what happens.
Br,
Tuomas
From: Quentin Hartman [mailto:[email protected]]
Sent: 7. elokuuta 2015 20:32
To: Tuomas Juntunen
Cc: ceph-users
Subject: Re: [ceph-users] Flapping OSD's when scrubbing
That kind of behavior is usually caused by the OSDs getting busy enough that
they aren't answering heartbeats in a timely fashion. It can also happen if you
have any netowrk flakiness and heartbeats are getting lost because of that.
I think (I'm not positive though) that increasing your heartbeat interval may
help. Also, looking at the number of threads you have for your OSDs, that seems
potentially problematic. If you've got 24 OSDs per machine and each one is
running 12 threads, that's 288 threads on 12 cores for just the requests. Plus
the disk threads, plus the filestore op threads... That level of thread
contention seems like it might be contributing to missing the heartbeats. But
again, that's conjecture. I've not worked with a setup as dense as yours.
QH
On Fri, Aug 7, 2015 at 11:21 AM, Tuomas Juntunen
<[email protected]> wrote:
Hi
We are experiencing an annoying problem where scrubs make OSD’s flap down and
cause Ceph cluster to be unusable for couple of minutes.
Our cluster consists of three nodes connected with 40gbit infiniband using
IPoIB, with 2x 6 core X5670 CPU’s and 64GB of memory
Each node has 6 SSD’s for journals to 12 OSD’s 2TB disks (Fast pools) and
another 12 OSD’s 4TB disks (Archive pools) which have journal on the same disk.
It seems that our cluster is constantly doing scrubbing, we rarely see only
active+clean, below is the status at the moment.
cluster a2974742-3805-4cd3-bc79-765f2bddaefe
health HEALTH_OK
monmap e16: 4 mons at
{lb1=10.20.60.1:6789/0,lb2=10.20.60.2:6789/0,nc1=10.20.50.2:6789/0,nc2=10.20.50.3:6789/0}
election epoch 1838, quorum 0,1,2,3 nc1,nc2,lb1,lb2
mdsmap e7901: 1/1/1 up {0=lb1=up:active}, 4 up:standby
osdmap e104824: 72 osds: 72 up, 72 in
pgmap v12941402: 5248 pgs, 9 pools, 19644 GB data, 4810 kobjects
59067 GB used, 138 TB / 196 TB avail
5241 active+clean
7 active+clean+scrubbing
When OSD’s go down, first the load on a node goes high during scrubbing and
after that some OSD’s go down and 30 secs, they are back up. They are not
really going down, but are marked as down. Then it takes around couple of
minutes for everything be OK again.
Any suggestion how to fix this? We can’t go to production while this behavior
exists.
Our config is below:
[global]
fsid = a2974742-3805-4cd3-bc79-765f2bddaefe
mon_initial_members = lb1,lb2,nc1,nc2
mon_host = 10.20.60.1,10.20.60.2,10.20.50.2,10.20.50.3
auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx
filestore_xattr_use_omap = true
osd pool default pg num = 128
osd pool default pgp num = 128
public network = 10.20.0.0/16
osd_op_threads = 12
osd_op_num_threads_per_shard = 2
osd_op_num_shards = 6
#osd_op_num_sharded_pool_threads = 25
filestore_op_threads = 12
ms_nocrc = true
filestore_fd_cache_size = 64
filestore_fd_cache_shards = 32
ms_dispatch_throttle_bytes = 0
throttler_perf_counter = false
mon osd min down reporters = 25
[osd]
osd scrub max interval = 1209600
osd scrub min interval = 604800
osd scrub load threshold = 3.0
osd max backfills = 1
osd recovery max active = 1
# IO Scheduler settings
osd scrub sleep = 1.0
osd disk thread ioprio class = idle
osd disk thread ioprio priority = 7
osd scrub chunk max = 1
osd scrub chunk min = 1
osd deep scrub stride = 1048576
filestore queue max ops = 10000
filestore max sync interval = 30
filestore min sync interval = 29
osd deep scrub interval = 2592000
osd heartbeat grace = 240
osd heartbeat interval = 12
osd mon report interval max = 120
osd mon report interval min = 5
osd_client_message_size_cap = 0
osd_client_message_cap = 0
osd_enable_op_tracker = false
osd crush update on start = false
[client]
rbd cache = true
rbd cache size = 67108864 # 64mb
rbd cache max dirty = 50331648 # 48mb
rbd cache target dirty = 33554432 # 32mb
rbd cache writethrough until flush = true # It's by default
rbd cache max dirty age = 2
admin socket = /var/run/ceph/$cluster-$type.$id.$pid.$cctid.asok
Br,
Tuomas
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