ceph var # mount | grep ceph
/dev/vdc on /var/lib/ceph type btrfs (rw)
ceph var # btrfs fi df /var/lib/ceph
Data: total=3.01GB, used=1.96GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=4.70MB
Metadata: total=8.00MB, used=0.00
ceph var # ceph -w
   health HEALTH_OK
   monmap e1: 1 mons at {a=10.13.37.4:6789/0}, election epoch 1, quorum 0 a
   osdmap e9: 2 osds: 2 up, 2 in
    pgmap v217: 576 pgs: 576 active+clean; 8730 bytes data, 4025 MB used, 32801 MB / 40960 MB avail
   mdsmap e9: 1/1/1 up {0=a=up:active}