ceph osd pool create ddd 64 64 replicated replicated_rule --cluster ceph
结果：
Error ERANGE: pg_num 64 size 3 would mean 939 total pgs, which exceeds max 750 (mon_max_pg_per_osd 250 * num_in_osds 3)
想知道这个939是如何计算的，我怎么设置才能小于750