In this chapter, we studied how to create a replica set from scratch to provide a readily available MongoDB server. First of all, we discussed the basic considerations of a replica set. Next, we configured the workspace to run the replica set. Additionally, we learned basic replica set commands in order to add or remove members from the replica set.

In our example, we had a three-member replica set, one primary and two secondary nodes. After configuration and setup, to test the replica set, we deactivated different nodes in the replica set. Also, we found that upon disabling the primary node, the replica set will choose another primary node from the active secondary members using an election process.

Also, we learned to run an arbiter node and add it to an existing replica set network. We found that arbiter nodes won't save and hold data at all.

In the next chapter, we will learn sharding in MongoDB, and distributing a dataset into different servers and machines.