The first method gives you the default value but it is only possible to execute that command on a node that is running a ceph daemon i.e. MON or OSD so this will not work in this case.
The second method can be run from the cinder node but, it gives the replication sizes in use for existing pools so (a) you assume that a pool already exists and (b) the sizes on existing pools may not be the default. This will not work either.
The only way to get the default would be to have the ceph node/service provide it when the relation is joined.
There are two ways to get replication sizes in uses:
1. sudo ceph --admin-daemon /var/run/ ceph/ceph- mon.a.asok config show| grep osd_pool_ default_ size
2. ceph osd dump| grep "rep size"
The first method gives you the default value but it is only possible to execute that command on a node that is running a ceph daemon i.e. MON or OSD so this will not work in this case.
The second method can be run from the cinder node but, it gives the replication sizes in use for existing pools so (a) you assume that a pool already exists and (b) the sizes on existing pools may not be the default. This will not work either.
The only way to get the default would be to have the ceph node/service provide it when the relation is joined.