If you deploy more than three OSDs on RHCS3 and set the PG number for your pools as determined by pgcalc (https://access.redhat.com/labs/cephpgc), deployment will fail because ceph-ansible creates pools before all OSDs are active. To avoid the problem, set the default PG number to 32 and when the deployment is finished, manually raise the PG number as described in the Storage Strategies Guide, https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/3/html/storage_strategies_guide/placement_groups_pgs#set_the_number_of_pgs.