On 03/03/2021 00:55, Lincoln Bryant wrote:
Hi list,
We recently had a cluster outage over the weekend where several OSDs were inaccessible over night for several hours. When I found the cluster in the morning, the monitors' root disks (which contained both the monitor's leveldb and the Ceph logs) had completely filled.
After restarting OSDs, cleaning out the monitors' logs, moving /var/lib/ceph to dedicated disks on the mons, and starting recovery (in which there was 1 unfound object that I marked lost, if that has any relevancy), the leveldb continued/continues to grow without bound. The cluster has all PGs in active+clean at this point, yet I'm accumulating what seems like approximately ~1GB/hr of new leveldb data.
Two of the monitors (a, c) are in quorum, while the third (b) has been synchronizing for the last several hours, but doesn't seem to be able to catch up. Mon 'b' has been running for 4 hours now in the 'synchronizing' state. The mon's log has many messages about compacting and deleting files, yet we never exit the synchronization state.
The ceph.log is also rapidly accumulating complaints that the mons are slow (not surprising, I suppose, since the levelDBs are ~100GB at this point).
I've found that using monstore tool to do compaction on mons 'a' and 'c' thelps but is only a temporary fix. Soon the database inflates again and I'm back to where I started.
Are all the PGs in the active+clean state? I don't assume so? This will
cause the MONs to keep a large history of OSDMaps in their DB and thus
it will keep growing.
Thoughts on how to proceed here? Some ideas I had:
- Would it help to add some new monitors that use RocksDB?
They would need to sync which can take a lot of time. Moving to RocksDB
is a good idea when this is all fixed.
- Stop a monitor and dump the keys via monstoretool, just to get an idea of what's going on?
- Increase mon_sync_max_payload_size to try to move data in larger chunks?
I would just try it.
- Drop down to a single monitor, and see if normal compaction triggers and stops growing unbounded?
It will keep growing, the compact only works for a limited time. Make
sure the PGs become clean again.
In the meantime make sure you have enough disk space.
Wido
- Stop both 'a' and 'c', compact them, start them, and immediately start 'b' ?
Appreciate any advice.
Regards,
Lincoln
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