Quick Introduction of Wired Tiger Storage Engine: It is the first pluggable storage engine, new in Mongodb 3.0. Stores data in B-tree while MMAPPV1 stores its indexes in B-tree not data. Wired tiger has two caches (Wired Tiger and File system) for performance improvement. Provides document level locking in short better concurrency than MMAPV1. From Mongodb Version 3.2 wired tiger is the default storage engine. Steps to replace existing MMAPV1 storage engine with Wired Tiger Storage Engine on Mongodb version: 3.0.4 We have already running mongod services with three members replica sets having default storage engine (MMAPV1): Here are three mongod processes: mongod --config /data/replset1/conf/rs_member.conf mongod --config /data/replset2/conf/rs_member.conf mongod --config /data/replset3/conf/rs_member.conf Note: If we directly try to restart mongod with –storageEngine parameter then we get fo...