Ceph

Balance the active and standby MDS daemons on available hosts automatically. See below for some background information.

Used cephadm to bootstrap a cluster.

The service configuration:

service_type: mds
service_id: test-fs
service_name: mds.test-fs
placement:
  count: 4
  hosts:
  - mdshost1.example.com
  - mdshost2.example.com

Commands used to create filesystem:

ceph fs volume create test-fs
ceph fs set test-fs max_mds 2

After the creation of the filesystem and setting the service configuration, an active and a standby MDS service where deployed on each node.
But after a reboot of the server mdshost2, the active daemons where all running on mdshost1 and all standby daemons where running on mdshost2. This didn't change, so I restarted a daemon on mdshost1 to have equally number of active and standby daemons on both hosts.