This isn't an answer, but a suggestion to try and help track it down as I'm
not sure what the problem is. Try querying the admin socket for your osds
and look through all of their config options and settings for something
that might explain why you have multiple deep scrubs happening on a single
osd at the same time.
However if you misspoke and only have 1 deep scrub per osd but multiple
people node, then what you are seeing is expected behavior. I believe that
luminous added a sleep seeing for scrub io that also might help. Looking
through the admin socket dump of settings looking for scrub should give you
some ideas of things to try.
On Tue, Sep 26, 2017, 2:04 PM J David <j.david.li...@gmail.com> wrote:
> With “osd max scrubs” set to 1 in ceph.conf, which I believe is also
> the default, at almost all times, there are 2-3 deep scrubs running.
>
> 3 simultaneous deep scrubs is enough to cause a constant stream of:
>
> mon.ceph1 [WRN] Health check update: 69 slow requests are blocked > 32
> sec (REQUEST_SLOW)
>
> This seems to correspond with all three deep scrubs hitting the same
> OSD at the same time, starving out all other I/O requests for that
> OSD. But it can happen less frequently and less severely with two or
> even one deep scrub running. Nonetheless, consumers of the cluster
> are not thrilled with regular instances of 30-60 second disk I/Os.
>
> The cluster is five nodes, 15 OSDs, and there is one pool with 512
> placement groups. The cluster is running:
>
> ceph version 12.2.0 (32ce2a3ae5239ee33d6150705cdb24d43bab910c) luminous
> (rc)
>
> All of the OSDs are bluestore, with HDD storage and SSD block.db.
>
> Even setting “osd deep scrub interval = 1843200” hasn’t resolved this
> issue, though it seems to get the number down from 3 to 2, which at
> least cuts down on the frequency of requests stalling out. With 512
> pgs, that should mean that one pg gets deep-scrubbed per hour, and it
> seems like a deep-scrub takes about 20 minutes. So what should be
> happening is that 1/3rd of the time there should be one deep scrub,
> and 2/3rds of the time there shouldn’t be any. Yet instead we have
> 2-3 deep scrubs running at all times.
>
> Looking at “ceph pg dump” shows that about 7 deep scrubs get launched per
> hour:
>
> $sudo ceph pg dump | fgrep active | awk ‘{print$23” “$24" "$1}' |
> fgrep 2017-09-26 | sort -rn | head -22
> dumped all
> 2017-09-26 16:42:46.781761 0.181
> 2017-09-26 16:41:40.056816 0.59
> 2017-09-26 16:39:26.216566 0.9e
> 2017-09-26 16:26:43.379806 0.19f
> 2017-09-26 16:24:16.321075 0.60
> 2017-09-26 16:08:36.095040 0.134
> 2017-09-26 16:03:33.478330 0.b5
> 2017-09-26 15:55:14.205885 0.1e2
> 2017-09-26 15:54:31.413481 0.98
> 2017-09-26 15:45:58.329782 0.71
> 2017-09-26 15:34:51.777681 0.1e5
> 2017-09-26 15:32:49.669298 0.c7
> 2017-09-26 15:01:48.590645 0.1f
> 2017-09-26 15:01:00.082014 0.199
> 2017-09-26 14:45:52.893951 0.d9
> 2017-09-26 14:43:39.870689 0.140
> 2017-09-26 14:28:56.217892 0.fc
> 2017-09-26 14:28:49.665678 0.e3
> 2017-09-26 14:11:04.718698 0.1d6
> 2017-09-26 14:09:44.975028 0.72
> 2017-09-26 14:06:17.945012 0.8a
> 2017-09-26 13:54:44.199792 0.ec
>
> What’s going on here?
>
> Why isn’t the limit on scrubs being honored?
>
> It would also be great if scrub I/O were surfaced in “ceph status” the
> way recovery I/O is, especially since it can have such a significant
> impact on client operations.
>
> Thanks!
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> ceph-users@lists.ceph.com
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>
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