[NFS-Ganesha-Support] Performance of RGW_FSAL vs CEPH_FSAL

Is the RGW_FSAL using the S3 API under the hood (aka sending S3 http requests)? Someone on my team is conjecturing that RGW_FSAL will be markedly slower than CEPH_FSAL on that basis. Does anyone have a sense of the average performance characteristics of these two FSALs?