Ceph CRUSH rules in map

Hi all, I have a question regarding following rules in Ceph CRUSH map: enum crush_opcodes { /*! do nothing */ CRUSH_RULE_NOOP = 0, CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */ CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */ /* arg2 = type */ CRUSH_RULE_CHOOSE_INDEP = 3, /* same */ CRUSH_RULE_EMIT = 4, /* no args */ CRUSH_RULE_CHOOSELEAF_FIRSTN = 6, CRUSH_RULE_CHOOSELEAF_INDEP = 7, CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */ CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */ CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10, CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11, CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12, CRUSH_RULE_SET_CHOOSELEAF_STABLE = 13 }; Can we skip specific rules ? Or lets say, what are the minimum number of rules required by CRUSH? Because my understanding is, it all depends on map hierarchy. If we have a particular/given hierarchy, we can skip certain rules?