Ceph/ODF: All MDS are up:standby, "mds: 0/1 daemons up (1 failed), 2 standby".

Issue

All MDS are up:standby, "mds: 0/1 daemons up (1 failed), 2 standby".

This example shows a system where there should be 1 Active MDS and 1 Standby MDS.

sh-5.1$ ceph status
  cluster:
    id:     [REDACTED]
    health: HEALTH_ERR
            1 filesystem is degraded
            1 filesystem has a failed mds daemon
            1 filesystem is offline

  services:
    mon: 3 daemons, quorum b,c,d (age 14h)
    mgr: a(active, since 11h), standbys: b
    mds: 0/1 daemons up (1 failed), 2 standby
    osd: 3 osds: 3 up (since 14h), 3 in (since 36h)
    rgw: 1 daemon active (1 hosts, 1 zones)

  data:
    volumes: 0/1 healthy, 1 failed
    pools:   12 pools, 169 pgs
    objects: 583 objects, 484 MiB
    usage:   2.0 GiB used, 30 TiB / 30 TiB avail
    pgs:     169 active+clean

For this solution to be applicable, these 3 conditions must exist.
See example in Diagnostic Steps section.

• Both MDS Servers are "up:standby".
• The MDS Filesystem is not damaged.
• The MDS logs show all MDS servers transitioning to "up:standby" without cause.