Ceph » CephFS

This is what we currently get when starting with vstart, which creates MDS daemons before creating the filesystem:

2018-04-26 07:02:50.411773 [INF]  daemon mds.b is now active in filesystem cephfs_a as rank 0 
2018-04-26 07:02:50.362801 [INF]  Cluster is now healthy 
2018-04-26 07:02:50.362769 [INF]  Health check cleared: MDS_UP_LESS_THAN_MAX (was: 1 filesystem is online with fewer MDS than max_mds) 
2018-04-26 07:02:50.362727 [INF]  Health check cleared: MDS_ALL_DOWN (was: 1 filesystem is offline) 
2018-04-26 07:02:50.362596 [INF]  daemon mds.b assigned to filesystem cephfs_a as rank 0 (now has 1 ranks) 
2018-04-26 07:02:49.342879 [WRN]  Health check failed: 1 filesystem is online with fewer MDS than max_mds (MDS_UP_LESS_THAN_MAX) 
2018-04-26 07:02:49.342839 [ERR]  Health check failed: 1 filesystem is offline (MDS_ALL_DOWN) 
2018-04-26 07:02:45.918532 [INF]  osd.0 172.21.9.34:6801/4312 boot 
2018-04-26 07:02:34.291164 [INF]  Manager daemon x is now available 
2018-04-26 07:02:34.267433 [INF]  Activating manager daemon x 
2018-04-26 07:02:31.616329 [INF]  mon.a is new leader, mons a in quorum (ranks 0) 

The user hasn't done anything wrong here: the MDSs are already running when the FS is created, so the FS should come up cleanly without generating any health errors or warnings.