When I upgraded version 3.0.12 replication set mode set under mongodb engine upgrade from MMAPv1 to WiredTiger, start a SECONDARY node when the node fails to pull data from other nodes from the resulting node can not start. Start command:" /home/worker/mongodb3.0/bin/mongod --storageEngine = wiredTiger -f /home/worker/mongodb3.0/conf/mongo.cnf". Strace analysis obtained by:" +++ killed by SIGKILL +++ information". See such a log and then view the / var / log / messages file: kernel: "Out of memory: Kill process 22373 (mongod) score 188 or sacrifice child".

Operating system is CentOS release 6.5, memory 8G. Replication set altogether three nodes are deployed in the same server. The other two have been successfully upgraded to WiredTiger engine,but upgraded the last one failed.