Thanks Sage!
ceph osd dump: https://pastebin.com/raw/zLPz9DQg 

ceph-monstore-tool /var/lib/ceph/mon/ceph-ufm03 dump-keys |grep osd_snap| cut -c-29 |uniq -c
      2 osd_snap / purged_snap_10_000
      1 osd_snap / purged_snap_12_000
     75 osd_snap / purged_snap_13_000
      4 osd_snap / purged_snap_14_000
 778106 osd_snap / purged_snap_15_000
    861 osd_snap / purged_snap_1_0000
    323 osd_snap / purged_snap_4_0000
     88 osd_snap / purged_snap_5_0000
      2 osd_snap / purged_snap_7_0000
      2 osd_snap / purged_snap_8_0000
      2 osd_snap / removed_epoch_10_0
      1 osd_snap / removed_epoch_12_0
     75 osd_snap / removed_epoch_13_0
      4 osd_snap / removed_epoch_14_0
2316417 osd_snap / removed_epoch_15_0
    970 osd_snap / removed_epoch_1_00
    324 osd_snap / removed_epoch_4_00
     89 osd_snap / removed_epoch_5_00
      2 osd_snap / removed_epoch_7_00
      2 osd_snap / removed_epoch_8_00
      2 osd_snap / removed_snap_10_00
      1 osd_snap / removed_snap_12_00
     75 osd_snap / removed_snap_13_00
      4 osd_snap / removed_snap_14_00
2720849 osd_snap / removed_snap_15_00
   1161 osd_snap / removed_snap_1_000
    379 osd_snap / removed_snap_4_000
     89 osd_snap / removed_snap_5_000
      2 osd_snap / removed_snap_7_000
      2 osd_snap / removed_snap_8_000

From: Sage Weil <sage@newdream.net>
Sent: Monday, September 23, 2019 9:41 AM
To: Koebbe, Brian <koebbe@wustl.edu>
Cc: ceph-users@ceph.io <ceph-users@ceph.io>; dev@ceph.io <dev@ceph.io>
Subject: Re: [ceph-users] Seemingly unbounded osd_snap keys in monstore. Normal? Expected?
 
Hi,

On Mon, 23 Sep 2019, Koebbe, Brian wrote:
> Our cluster has a little over 100 RBDs.  Each RBD is snapshotted with a typical "frequently", hourly, daily, monthly type of schedule.
> A while back a 4th monitor was temporarily added to the cluster that took hours to synchronize with the other 3.
> While trying to figure out why that addition took so long, we discovered that our monitors have what seems like a really large number of osd_snap keys:
>
> ​ceph-monstore-tool /var/lib/ceph/mon/xxxxxx dump-keys |awk '{print $1}'|uniq -c
>     153 auth
>       2 config
>      10 health
>    1441 logm
>       3 mdsmap
>     313 mgr
>       1 mgr_command_descs
>       3 mgr_metadata
>     163 mgrstat
>       1 mkfs
>     323 mon_config_key
>       1 mon_sync
>       6 monitor
>       1 monitor_store
>      32 monmap
>     120 osd_metadata
>       1 osd_pg_creating
> 5818618 osd_snap
>   41338 osdmap
>     754 paxos
>
> A few questions:
>
> Could this be the cause of the slow addition/synchronization?

Probably!

> Is what looks like an unbounded number of osd_snaps expected?

Maybe.  Can you send me the output of 'ceph osd dump'?  Also, if you don't
mind doing the dump above and grepping out just the osd_snap keys, so I
can see what they look like and if they match the osd map contents?

Thanks!
sage


> If trimming/compacting them would help, how would one do that?
>
> Thanks,
> Brian
>
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