We are getting the same log message as you, but not too often, and from what I gathered it is normal to see that.
Not sure how often you are seeing those.
How many disks are connected to that VM? Take a look in /proc/pid/fd and count the file descriptors, then compare that to /proc/pid/limits. My first guess is the problem is in here. Basicaly qemu needs to make a connection to every VM hosting the PGs the RBD image is on, and that could be thousands (and since you have close to 500 osds I guess you are hitting that limit much sooner than most folks).
Jan
> On 15 Jul 2015, at 10:23, Jeya Ganesh Babu Jegatheesan <jjeya@xxxxxxxxxxx> wrote:
>
>
>
> 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
>>>
>>> _______________________________________________
>>> ceph-users mailing list
>>> ceph-users@xxxxxxxxxxxxxx
>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
>
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
