. 1 oplogsize size configuration:
2 availability mongodb embodiment constructed replica set, a minimum of three nodes, a primary node master, from a Slave node, a node arbitration election arbiter. When the master node Ben collapse, the arbitration node election to take over from the primary node node, continue to provide data services to ensure high availability. Replica diversity scheme, the data is saved from the node, his data from the master node is synchronized from, and mysql bin-log from a similar manner as the master copy, MongoDB uses to synchronize data from the master node according oplog. oplog not infinite, if the default is not manually set, then oplogSize is 5% of the disk space. % More than 5 , oplog will be overwritten.
3 Start node, a node then just log in through the mongo shell, this time, did not show any information node replica set, when we set by rs.initiate (cfg), the master node will slowly become OTHER-> SECONDARY -> PRIMARY