CephFS constant high write I/O to the metadata pool

[olliRJL]

Hi,

I'm seeing constant 25-50MB/s writes to the metadata pool even when all clients and the cluster is idling and in clean state. This surely can't be normal?

Even with this write rate everything does run smooth but it annoys to see this constant high write happening.

The setup:
- a hyperconverged 3 node core cluster (1 active and 2 standby MDS) + 6 storage nodes
- alltogether 12 SSD OSDs, 24 HDD OSDs, 12 NVMe OSDs
- Ceph 16.2.9

Any ideas where to look at?
Cheers!
o.