Re: All PGs are active+clean, still remapped PGs

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On Wed, 2 Nov 2016, Wido den Hollander wrote:
> 
> > Op 2 november 2016 om 14:30 schreef Sage Weil <sage@xxxxxxxxxxxx>:
> > 
> > 
> > On Wed, 2 Nov 2016, Wido den Hollander wrote:
> > > 
> > > > Op 26 oktober 2016 om 11:18 schreef Wido den Hollander <wido@xxxxxxxx>:
> > > > 
> > > > 
> > > > 
> > > > > Op 26 oktober 2016 om 10:44 schreef Sage Weil <sage@xxxxxxxxxxxx>:
> > > > > 
> > > > > 
> > > > > On Wed, 26 Oct 2016, Dan van der Ster wrote:
> > > > > > On Tue, Oct 25, 2016 at 7:06 AM, Wido den Hollander <wido@xxxxxxxx> wrote:
> > > > > > >
> > > > > > >> Op 24 oktober 2016 om 22:29 schreef Dan van der Ster <dan@xxxxxxxxxxxxxx>:
> > > > > > >>
> > > > > > >>
> > > > > > >> Hi Wido,
> > > > > > >>
> > > > > > >> This seems similar to what our dumpling tunables cluster does when a few
> > > > > > >> particular osds go down... Though in our case the remapped pgs are
> > > > > > >> correctly shown as remapped, not clean.
> > > > > > >>
> > > > > > >> The fix in our case will be to enable the vary_r tunable (which will move
> > > > > > >> some data).
> > > > > > >>
> > > > > > >
> > > > > > > Ah, as I figured. I will probably apply the Firefly tunables here. This cluster was upgraded from Dumping to Firefly and to Hammer recently and we didn't change the tunables yet.
> > > > > > >
> > > > > > > The MON stores are 35GB each right now and I think they are not trimming due to the pg_temp which still exists.
> > > > > > >
> > > > > > > I'll report back later, but this rebalance will take a lot of time.
> > > > > > 
> > > > > > I forgot to mention, a workaround for the vary_r issue is to simply
> > > > > > remove the down/out osd from the crush map. We just hit this issue
> > > > > > again last night on a failed osd and after removing it from the crush
> > > > > > map the last degraded PG started backfilling.
> > > > > 
> > > > > Also note that if you do enable vary_r, you can set it to a higher value 
> > > > > (like 5) to get the benefit without moving as much existing data.  See the 
> > > > > CRUSH tunable docs for more details!
> > > > > 
> > > > 
> > > > Yes, thanks. So with the input here we have a few options and are deciding which routes to take.
> > > > 
> > > > The cluster is rather old (hw as well), so we have to be careful at this time. For the record, our options are:
> > > > 
> > > > - vary_r to 1: 73% misplaced
> > > > - vary_r to 2 ~ 4: Looking into it
> > > > - Removing dead OSDs from CRUSH
> > > > 
> > > > As the cluster is under some stress we have to do this in the weekends, that makes it a bit difficult, but nothing we can't overcome.
> > > > 
> > > > Thanks again for the input and I'll report on what we did later on.
> > > > 
> > > 
> > > So, what I did:
> > > - Remove all dead OSDs from the CRUSHMap and OSDMap
> > > - Set vary_r to 2
> > > 
> > > This resulted in:
> > > 
> > > osdmap e119647: 169 osds: 166 up, 166 in; 6 remapped pgs
> > > 
> > > pg_temp 4.39 [160,17,10,8]
> > > pg_temp 4.2c9 [164,95,10,7]
> > > pg_temp 4.816 [167,147,57,2]
> > > pg_temp 4.862 [31,160,138,2]
> > > pg_temp 4.a83 [156,83,10,7]
> > > pg_temp 4.e8e [164,78,10,8]
> > > 
> > > In this case, osd 2 and 10 no longer exist, not in the OSDMap nor in the CRUSHMap.
> > > 
> > > root@mon1:~# ceph osd metadata 2
> > > Error ENOENT: osd.2 does not exist
> > > root@mon1:~# ceph osd metadata 10
> > > Error ENOENT: osd.10 does not exist
> > > root@mon1:~# ceph osd find 2
> > > Error ENOENT: osd.2 does not exist
> > > root@mon1:~# ceph osd find 10
> > > Error ENOENT: osd.10 does not exist
> > > root@mon1:~#
> > > 
> > > Looking at PG '4.39' for example, a query tells me:
> > > 
> > >     "up": [
> > >         160,
> > >         17,
> > >         8
> > >     ],
> > >     "acting": [
> > >         160,
> > >         17,
> > >         8
> > >     ],
> > > 
> > > So I really wonder there the pg_temp with osd.10 comes from.
> > 
> > Hmm.. are the others also the same like that?  You can manually poke 
> > it into adjusting pg-temp with
> > 
> >  ceph osd pg_temp <pgid> <just the primary osd>
> > 
> > That'll make peering reevaluate what pg_temp it wants (if any).  It might 
> > be that it isn't noticing that pg_temp matches acting.. but the mon has 
> > special code to remove those entries, so hrm.  Is this hammer?
> > 
> 
> So yes, that worked. I did it for 3 PGs:
> 
> # ceph osd pg-temp 4.39 160
> # ceph osd pg-temp 4.2c9 164
> # ceph osd pg-temp 4.816 167
> 
> Now my pg_temp looks like:
> 
> pg_temp 4.862 [31,160,138,2]
> pg_temp 4.a83 [156,83,10,7]
> pg_temp 4.e8e [164,78,10,8]
> 
> There we see the osd.2 and osd.10 again. I'm not setting these yet since you might want logs from the MONs or OSDs?
> 
> This is Hammer 0.94.9

I'm pretty sure this is a race condition that got cleaned up as part of 
https://github.com/ceph/ceph/pull/9078/commits.  The mon only checks the 
pg_temp entries that are getting set/changed, and since those are already 
in place it doesn't recheck them.  Any poke to the cluster that triggers 
peering ought to be enough to clear it up.  So, no need for logs, thanks!

We could add a special check during, say, upgrade, but generally the PGs 
will re-peer as the OSDs restart anyway and that will clear it up.

Maybe you can just confirm that marking an osd down (say, ceph osd down 
31) is also enough to remove the stray entry?

Thanks!
sage

 > 
> > > Setting vary_r to 1 will result in a 76% degraded state for the cluster 
> > > and I'm trying to avoid that (for now).
> > > 
> > > I restarted the Primary OSDs for all the affected PGs, but that didn't 
> > > help either.
> > > 
> > > Any bright ideas on how to fix this?
> > 
> > This part seems unrelated to vary_r... you shouldn't have to 
> > reduce it further!
> > 
> 
> Indeed, like you said, the pg_temp fixed it for 3 PGs already. Holding off with the rest in case you want logs or debug it further.
> 
> Wido
> 
> > sage
> > 
> > 
> > > 
> > > Wido
> > > 
> > > > Wido 
> > > > 
> > > > > sage
> > > > > 
> > > > > 
> > > > > > 
> > > > > > Cheers, Dan
> > > > > > 
> > > > > > 
> > > > > > >
> > > > > > > Wido
> > > > > > >
> > > > > > >> Cheers, Dan
> > > > > > >>
> > > > > > >> On 24 Oct 2016 22:19, "Wido den Hollander" <wido@xxxxxxxx> wrote:
> > > > > > >> >
> > > > > > >> > Hi,
> > > > > > >> >
> > > > > > >> > On a cluster running Hammer 0.94.9 (upgraded from Firefly) I have 29
> > > > > > >> remapped PGs according to the OSDMap, but all PGs are active+clean.
> > > > > > >> >
> > > > > > >> > osdmap e111208: 171 osds: 166 up, 166 in; 29 remapped pgs
> > > > > > >> >
> > > > > > >> > pgmap v101069070: 6144 pgs, 2 pools, 90122 GB data, 22787 kobjects
> > > > > > >> >     264 TB used, 184 TB / 448 TB avail
> > > > > > >> >         6144 active+clean
> > > > > > >> >
> > > > > > >> > The OSDMap shows:
> > > > > > >> >
> > > > > > >> > root@mon1:~# ceph osd dump|grep pg_temp
> > > > > > >> > pg_temp 4.39 [160,17,10,8]
> > > > > > >> > pg_temp 4.52 [161,16,10,11]
> > > > > > >> > pg_temp 4.8b [166,29,10,7]
> > > > > > >> > pg_temp 4.b1 [5,162,148,2]
> > > > > > >> > pg_temp 4.168 [95,59,6,2]
> > > > > > >> > pg_temp 4.1ef [22,162,10,5]
> > > > > > >> > pg_temp 4.2c9 [164,95,10,7]
> > > > > > >> > pg_temp 4.330 [165,154,10,8]
> > > > > > >> > pg_temp 4.353 [2,33,18,54]
> > > > > > >> > pg_temp 4.3f8 [88,67,10,7]
> > > > > > >> > pg_temp 4.41a [30,59,10,5]
> > > > > > >> > pg_temp 4.45f [47,156,21,2]
> > > > > > >> > pg_temp 4.486 [138,43,10,7]
> > > > > > >> > pg_temp 4.674 [59,18,7,2]
> > > > > > >> > pg_temp 4.7b8 [164,68,10,11]
> > > > > > >> > pg_temp 4.816 [167,147,57,2]
> > > > > > >> > pg_temp 4.829 [82,45,10,11]
> > > > > > >> > pg_temp 4.843 [141,34,10,6]
> > > > > > >> > pg_temp 4.862 [31,160,138,2]
> > > > > > >> > pg_temp 4.868 [78,67,10,5]
> > > > > > >> > pg_temp 4.9ca [150,68,10,8]
> > > > > > >> > pg_temp 4.a83 [156,83,10,7]
> > > > > > >> > pg_temp 4.a98 [161,94,10,7]
> > > > > > >> > pg_temp 4.b80 [162,88,10,8]
> > > > > > >> > pg_temp 4.d41 [163,52,10,6]
> > > > > > >> > pg_temp 4.d54 [149,140,10,7]
> > > > > > >> > pg_temp 4.e8e [164,78,10,8]
> > > > > > >> > pg_temp 4.f2a [150,68,10,6]
> > > > > > >> > pg_temp 4.ff3 [30,157,10,7]
> > > > > > >> > root@mon1:~#
> > > > > > >> >
> > > > > > >> > So I tried to restart osd.160 and osd.161, but that didn't chance the
> > > > > > >> state.
> > > > > > >> >
> > > > > > >> > root@mon1:~# ceph pg 4.39 query
> > > > > > >> > {
> > > > > > >> >     "state": "active+clean",
> > > > > > >> >     "snap_trimq": "[]",
> > > > > > >> >     "epoch": 111212,
> > > > > > >> >     "up": [
> > > > > > >> >         160,
> > > > > > >> >         17,
> > > > > > >> >         8
> > > > > > >> >     ],
> > > > > > >> >     "acting": [
> > > > > > >> >         160,
> > > > > > >> >         17,
> > > > > > >> >         8
> > > > > > >> >     ],
> > > > > > >> >     "actingbackfill": [
> > > > > > >> >         "8",
> > > > > > >> >         "17",
> > > > > > >> >         "160"
> > > > > > >> >     ],
> > > > > > >> >
> > > > > > >> > In all these PGs osd.10 is involved, but that OSD is down and out. I
> > > > > > >> tried marking it as down again, but that didn't work.
> > > > > > >> >
> > > > > > >> > I haven't tried removing osd.10 yet from the CRUSHMap since that will
> > > > > > >> trigger a rather large rebalance.
> > > > > > >> >
> > > > > > >> > This cluster is still running with the Dumpling tunables though, so that
> > > > > > >> might be the issue. But before I trigger a very large rebalance I wanted to
> > > > > > >> check if there are any insights on this one.
> > > > > > >> >
> > > > > > >> > Thanks,
> > > > > > >> >
> > > > > > >> > Wido
> > > > > > >> > _______________________________________________
> > > > > > >> > 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
> > > 
> > >
> 
> 
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