在local庫中不僅有主從日志 oplog集合，還有一個集合用於記錄主從配置信息 system.replset：
> use local
> show collections
> db.system.replset.find()
rs1:PRIMARY> use localuse local
switched to db local
rs1:PRIMARY> show collectionsshow collections
me
oplog.rs
replset.election
startup_log
system.replset
rs1:PRIMARY> db.system.replset.find()db.system.replset.find()
{ "_id" : "rs1", "version" : 1, "protocolVersion" : NumberLong(1), "members" : [ { "_id" : 0, "host" : "localhost:28010", "arbiterOnly" : false, "buildIndexes" : true, "hidden" : false, "priority" : 1, "tags" : { }, "slaveDelay" : NumberLong(0), "votes" : 1 }, { "_id" : 1, "host" : "localhost:28011", "arbiterOnly" : false, "buildIndexes" : true, "hidden" : false, "priority" : 1, "tags" : { }, "slaveDelay" : NumberLong(0), "votes" : 1 }, { "_id" : 2, "host" : "localhost:28012", "arbiterOnly" : false, "buildIndexes" : true, "hidden" : false, "priority" : 1, "tags" : { }, "slaveDelay" : NumberLong(0), "votes" : 1 } ], "settings" : { "chainingAllowed" : true, "heartbeatIntervalMillis" : 2000, "heartbeatTimeoutSecs" : 10, "electionTimeoutMillis" : 10000, "getLastErrorModes" : { }, "getLastErrorDefaults" : { "w" : 1, "wtimeout" : 0 }, "replicaSetId" : ObjectId("5791ea00a9dbf7228bb1ec0c") } }
rs1:PRIMARY>
從這個集合中可以看出，Replica Sets的配置信息，也可從任何已有成員實例上執行 rs.conf() 來查看信息。