StorageClass and Headless Service Configuration for MongoDB Replica Set

![](https://lh4.googleusercontent.com/ohALxLD4Ugj5FCwWqgqZ4xP9al4lTgrPDc9HsgPWYRZRz_buuYK6LKSC7A5n98DdOO-Po3Zq77Yt43-QhTWdIaXqltHI7PX0zMXAXbpiilYgdowGZapG0lJ9lgubwBj1CwNHHtXA) Let’s examine each piece in more detail. **StorageClass** The storage class tells Kubernetes what kind of storage to use for the database nodes. You can set up many different types of StorageClasses in a ton of different environments. For example, if you run Kubernetes in your own datacenter, you can use [GlusterFS](https://www.gluster.org/). On GCP, your [storage choices](https://cloud.google.com/compute/docs/disks/) are SSDs and hard disks. There are currently drivers for [AWS](/docs/user-guide/persistent-volumes/#aws), [Azure](/docs/user-guide/persistent-volumes/#azure-disk), [Google Cloud](/docs/user-guide/persistent-volumes/#gce), [GlusterFS](/docs/user-guide/persistent-volumes/#glusterfs), [OpenStack Cinder](/docs/user-guide/persistent-volumes/#openstack-cinder), [vSphere](/docs/user-guide/persistent-volumes/#vsphere), [Ceph RBD](/docs/user-guide/persistent-volumes/#ceph-rbd), and [Quobyte](/docs/user-guide/persistent-volumes/#quobyte). The configuration for the StorageClass looks like this: ```yaml kind: StorageClass apiVersion: storage.k8s.io/v1beta1 metadata: name: fast provisioner: kubernetes.io/gce-pd parameters: type: pd-ssd ``` This configuration creates a new StorageClass called “fast” that is backed by SSD volumes. The StatefulSet can now request a volume, and the StorageClass will automatically create it! Deploy this StorageClass: ``` kubectl apply -f googlecloud\_ssd.yaml ``` **Headless Service** Now you have created the Storage Class, you need to make a Headless Service. These are just like normal Kubernetes Services, except they don’t do any load balancing for you. When combined with StatefulSets, they can give you unique DNS addresses that let you directly access the pods! This is perfect for creating MongoDB replica sets, because our app needs to connect to all of the MongoDB nodes individually. The configuration for the Headless Service looks like this: ```yaml apiVersion: v1 kind: Service metadata: name: mongo labels: name: mongo

This section details the StorageClass and Headless Service components required for setting up a MongoDB replica set on Kubernetes. The StorageClass, configured to use SSD volumes, enables the StatefulSet to automatically create storage volumes. A Headless Service is then introduced, providing unique DNS addresses for direct access to the pods, which is necessary for creating MongoDB replica sets where the application connects to individual MongoDB nodes.