The documentation states: https://docs.ceph.com/docs/mimic/rados/operations/monitoring/ The POOLS section of the output provides a list of pools and the notional usage of each pool. The output from this section DOES NOT reflect replicas, clones or snapshots. For example, if you store an object with 1MB of data, the notional usage will be 1MB, but the actual usage may be 2MB or more depending on the number of replicas, clones and snapshots. However in our case we are clearly seeing the USAGE field multiplying the total object sizes to the number of replicas. [root@blackmirror ~]# ceph df RAW STORAGE: CLASS SIZE AVAIL USED RAW USED %RAW USED hdd 80 TiB 34 TiB 46 TiB 46 TiB 58.10 TOTAL 80 TiB 34 TiB 46 TiB 46 TiB 58.10 POOLS: POOL ID STORED OBJECTS USED %USED MAX AVAIL one 2 15 TiB 4.05M 46 TiB 68.32 7.2 TiB bench 5 250 MiB 67 250 MiB 0 22 TiB [root@blackmirror ~]# rbd du -p one NAME PROVISIONED USED ... <TOTAL> 20 TiB 15 TiB This is causing several apps (including ceph dashboard) to display inaccurate percentages, because they calculate the total pool capacity as USED + MAX AVAIL, which in this case yields 53.2TB, which is way off. 7.2TB is about 13% of that, so we receive alarms and this is bugging us for quite some time now.