Comment 3 for bug 2065470

"0" is explicitly set to the glance charm for example.

$ juju config -m openstack glance ceph-osd-replication-count
-> 0

And it's likely from this logic.
https://github.com/canonical/snap-openstack/blob/599e01aa263729d8f411241531bc424934b9ce05/sunbeam-python/sunbeam/commands/openstack.py#L139-L153

I have one OSD at least since I'm in the bootstrap phase. I will dig further why it's considered as 0.

$ sudo ceph status
  cluster:
    id: 78bb216d-fa9a-4938-b32b-6ac1f43448e9
    health: HEALTH_WARN
            1 pool(s) have no replicas configured

  services:
    mon: 1 daemons, quorum sunbeam-1 (age 2h)
    mgr: sunbeam-1(active, since 2h)
    osd: 1 osds: 1 up (since 2h), 1 in (since 2h)

  data:
    pools: 1 pools, 1 pgs
    objects: 2 objects, 449 KiB
    usage: 27 MiB used, 16 GiB / 16 GiB avail
    pgs: 1 active+clean