At MongoLab we manage thousands of MongoDB clusters and regularly help customers optimize system performance. Some of the best tools available for gaining insight into our MongoDB deployments are the monitoring features of MongoDB Management Service (MMS). MMS allows us to quickly determine the health of a MongoDB system and identify the root cause of performance issues. This post covers our general approach to using MMS and MongoDB log files and provides techniques to help you optimize your own MongoDB deployment, whether you’re in the cloud or on your own hardware.
First, we will define the key metrics that we use to guide any performance investigation. Then we will go through the various combinations of metric values, discuss what they mean, and explore how to address the problems they indicate.