On 7/15/15, 12:17 AM, "Jan Schermer" <jan@xxxxxxxxxxx> wrote:
>Do you have a comparison of the same workload on a different storage than
>CEPH?
I dont have a direct comparison data with a different storage. I did ran
similar workload with single VM which was booted off from a local disk and
i didn't see any issue. But as it was a from a local disk(single disk),
the performance was not comparable with the one with Ceph.
>
>I am asking because those messages indicate slow request - basically some
>operation took 120s (which would look insanely high to a storage
>administrator, but is sort of expected in a cloud environment). And even
>on a regular direct attached storage, some OPs can take that look but
>those issues are masked in drivers (they don¹t necessarily manifest as
>³task blocked² or ³soft lockups² but just as 100% iowait for periods of
>time - which is considered normal under load).
>
>In other words - are you seeing a real problem with your workload or just
>the messages?
The issue is that the access to the volumes gets stuck and never recovers.
The jbd2 kernel thread locks up. The system recovers only after a reboot.
>
>If you don¹t have any slow ops then you either have the warning set to
>high, or those blocked operations consist of more than just one OP - it
>adds up.
>
>It could also be caused by a network problem (like misconfigured offloads
>on network cards causing retransmissions/reorders and such) or if for
>example you run out of file desriptors on either the client or server
>side, it manifests as some requests getting stuck _without_ getting any
>slow ops on the ceph cluster side.
Yes, we are checking the network as well. Btw i see the following messages
in the osd logs (somewhere around 5-6 message for the day per osd), could
this point that there is some network issue? would this cause a write to
get stuck?
ceph-osd.296.log:2015-07-14 19:17:04.907107 7ffd1fc43700 0 --
10.163.45.3:6893/2046 submit_message osd_op_reply(562032
rbd_data.2f982f3c214f5
9de.000000000000003d [stat,set-alloc-hint object_size 4194304 write_size
4194304,write 1253376~4096] v54601'407287 uv407287 ack = 0) v6 remote
, 10.163.43.1:0/1076109, failed lossy con, dropping message 0x11cd5600
2015-07-14 17:35:24.209722 7ffc67c4d700 0 -- 10.163.45.3:6893/2046 >>
10.163.42.14:0/1004886 pipe(0x18521c80 sd=255 :6893 s=0 pgs=0 cs=0 l=1
c=0xd86a680).accept
replacing existing (lossy) channel (new one lossy=1)
>
>
>And an obligatory question - you say your OSDs don¹t use much CPU, but
>how are the disks? Aren¹t some of them 100% utilized when this happens?
Disk as well are not fully utilized, the iops and bandwidth are quite low.
The load as such is evenly distributed across the disks.
>
>Jan
>
>> On 15 Jul 2015, at 02:23, Jeya Ganesh Babu Jegatheesan
>><jjeya@xxxxxxxxxxx> wrote:
>>
>>
>>
>> On 7/14/15, 4:56 PM, "ceph-users on behalf of Wido den Hollander"
>> <ceph-users-bounces@xxxxxxxxxxxxxx on behalf of wido@xxxxxxxx> wrote:
>>
>>> On 07/15/2015 01:17 AM, Jeya Ganesh Babu Jegatheesan wrote:
>>>> Hi,
>>>>
>>>> We have a Openstack + Ceph cluster based on Giant release. We use ceph
>>>> for the VMs volumes including the boot volumes. Under load, we see the
>>>> write access to the volumes stuck from within the VM. The same would
>>>> work after a VM reboot. The issue is seen with and without rbd cache.
>>>> Let me know if this is some known issue and any way to debug further.
>>>> The ceph cluster itself seems to be clean. We have currently disabled
>>>> scrub and deep scrub. 'ceph -s' output as below.
>>>>
>>>
>>> Are you seeing slow requests in the system?
>>
>> I dont see slow requests in the cluster.
>>
>>>
>>> Are any of the disks under the OSDs 100% busy or close to it?
>>
>> Most of the OSDs use 20% of a core. There is no OSD process busy at
>>100%.
>>
>>>
>>> Btw, the amount of PGs is rather high. You are at 88, while the formula
>>> recommends:
>>>
>>> num_osd * 100 / 3 = 14k (cluster total)
>>
>> We used 30 * num_osd per pool. We do have 4 pools, i believe thats the
>>why
>> the PG seems to be be high.
>>
>>>
>>> Wido
>>>
>>>> cluster eaaeaa55-a8e7-4531-a5eb-03d73028b59d
>>>> health HEALTH_WARN noscrub,nodeep-scrub flag(s) set
>>>> monmap e71: 9 mons at
>>>>
>>>>{gngsvc009a=10.163.43.1:6789/0,gngsvc009b=10.163.43.2:6789/0,gngsvc010a
>>>>=1
>>>>
>>>>0.163.43.5:6789/0,gngsvc010b=10.163.43.6:6789/0,gngsvc011a=10.163.43.9:
>>>>67
>>>>
>>>>89/0,gngsvc011b=10.163.43.10:6789/0,gngsvc011c=10.163.43.11:6789/0,gngs
>>>>vm
>>>> 010d=10.163.43.8:6789/0,gngsvm011d=10.163.43.12:6789/0}, election
>>>>epoch
>>>> 22246, quorum 0,1,2,3,4,5,6,7,8
>>>>
>>>>gngsvc009a,gngsvc009b,gngsvc010a,gngsvc010b,gngsvm010d,gngsvc011a,gngsv
>>>>c0
>>>> 11b,gngsvc011c,gngsvm011d
>>>> osdmap e54600: 425 osds: 425 up, 425 in
>>>> flags noscrub,nodeep-scrub
>>>> pgmap v13257438: 37620 pgs, 4 pools, 134 TB data, 35289 kobjects
>>>> 402 TB used, 941 TB / 1344 TB avail
>>>> 37620 active+clean
>>>> client io 94059 kB/s rd, 313 MB/s wr, 4623 op/s
>>>>
>>>>
>>>> The traces we see in the VM's kernel are as below.
>>>>
>>>> [ 1080.552901] INFO: task jbd2/vdb-8:813 blocked for more than 120
>>>> seconds.
>>>> [ 1080.553027] Tainted: GF O 3.13.0-34-generic
>>>> #60~precise1-Ubuntu
>>>> [ 1080.553157] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>>>> disables this message.
>>>> [ 1080.553295] jbd2/vdb-8 D ffff88003687e3e0 0 813 2
>>>> 0x00000000
>>>> [ 1080.553298] ffff880444fadb48 0000000000000002 ffff880455114440
>>>> ffff880444fadfd8
>>>> [ 1080.553302] 0000000000014440 0000000000014440 ffff88044a9317f0
>>>> ffff88044b7917f0
>>>> [ 1080.553303] ffff880444fadb48 ffff880455114cd8 ffff88044b7917f0
>>>> ffffffff811fc670
>>>> [ 1080.553307] Call Trace:
>>>> [ 1080.553309] [<ffffffff811fc670>] ? __wait_on_buffer+0x30/0x30
>>>> [ 1080.553311] [<ffffffff8175b8b9>] schedule+0x29/0x70
>>>> [ 1080.553313] [<ffffffff8175b98f>] io_schedule+0x8f/0xd0
>>>> [ 1080.553315] [<ffffffff811fc67e>] sleep_on_buffer+0xe/0x20
>>>> [ 1080.553316] [<ffffffff8175c052>] __wait_on_bit+0x62/0x90
>>>> [ 1080.553318] [<ffffffff811fc670>] ? __wait_on_buffer+0x30/0x30
>>>> [ 1080.553320] [<ffffffff8175c0fc>] out_of_line_wait_on_bit+0x7c/0x90
>>>> [ 1080.553322] [<ffffffff810aff70>] ?
>>>>wake_atomic_t_function+0x40/0x40
>>>> [ 1080.553324] [<ffffffff811fc66e>] __wait_on_buffer+0x2e/0x30
>>>> [ 1080.553326] [<ffffffff8129806b>]
>>>> jbd2_journal_commit_transaction+0x136b/0x1520
>>>> [ 1080.553329] [<ffffffff810a1f75>] ? sched_clock_local+0x25/0x90
>>>> [ 1080.553331] [<ffffffff8109a7b8>] ? finish_task_switch+0x128/0x170
>>>> [ 1080.553333] [<ffffffff8107891f>] ? try_to_del_timer_sync+0x4f/0x70
>>>> [ 1080.553334] [<ffffffff8129c5d8>] kjournald2+0xb8/0x240
>>>> [ 1080.553336] [<ffffffff810afef0>] ? __wake_up_sync+0x20/0x20
>>>> [ 1080.553338] [<ffffffff8129c520>] ? commit_timeout+0x10/0x10
>>>> [ 1080.553340] [<ffffffff8108fa79>] kthread+0xc9/0xe0
>>>> [ 1080.553343] [<ffffffff8108f9b0>] ? flush_kthread_worker+0xb0/0xb0
>>>> [ 1080.553346] [<ffffffff8176827c>] ret_from_fork+0x7c/0xb0
>>>> [ 1080.553349] [<ffffffff8108f9b0>] ? flush_kthread_worker+0xb0/0xb0
>>>>
>>>> Thanks,
>>>> Jeyaganesh.
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> ceph-users mailing list
>>>> ceph-users@xxxxxxxxxxxxxx
>>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>>>
>>>
>>>
>>> --
>>> Wido den Hollander
>>> 42on B.V.
>>> Ceph trainer and consultant
>>>
>>> Phone: +31 (0)20 700 9902
>>> Skype: contact42on
>>> _______________________________________________
>>> ceph-users mailing list
>>> ceph-users@xxxxxxxxxxxxxx
>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
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>
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