The following two queries show the total capacity of bytes in the cluster and the number of bytes used. They can be used to generate a pie chart in Grafana to show the percentage of used space. Note that these counters show the raw capacity before replication:

maxSeries(collectd.mon*.ceph.mon.mon*.ceph_bytes.Cluster.osdBytes)

maxSeries(collectd.mon*.ceph.mon.mon*.ceph_bytes.Cluster.osdBytesUsed)