[ceph-users] What could cause mon_osd_full_ratio to be exceeded?

Gregory Farnum gfarnum at redhat.com
Mon Nov 26 08:27:21 PST 2018

On Mon, Nov 26, 2018 at 10:28 AM Vladimir Brik
<vladimir.brik at icecube.wisc.edu> wrote:
> Hello
> I am doing some Ceph testing on a near-full cluster, and I noticed that,
> after I brought down a node, some OSDs' utilization reached
> osd_failsafe_full_ratio (97%). Why didn't it stop at mon_osd_full_ratio
> (90%) if mon_osd_backfillfull_ratio is 90%?

While I believe the very newest Ceph source will do this, it can be
surprisingly difficult to identify the exact size a PG will take up on
disk (thanks to omap/RocksDB data), and so for a long time we pretty
much didn't try — these ratios were checked when starting a backfill,
but we didn't try to predict where they would end up and limit
ourselves based on that.

> Thanks,
> Vlad
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