pve7to8, ceph pacific-to-quincy how do I discover the fs_name?

in https://pve.proxmox.com/wiki/Ceph_Pacific_to_Quincy

Disable standby_replay
ceph fs set <fs_name> allow_standby_replay false

Which....how do I discover the fs_name?

from https://docs.ceph.com/en/latest/cephfs/administration/

ceph fs ls

List all file systems by name.

when I do this as root on all my pve nodes:

root@pve3:~# ceph fs ls
No filesysystems enabled.

I'm at a loss. What next?

thanks!