Optimally combine Kubernetes and Ceph with Rook

Castling

What's Going On?

If you are used to working with Ceph, the various tools that provide insight into a running Ceph cluster can be used with Rook, too. However, you do need to launch a Pod especially for these tools in the form of the Rook Toolbox.

A CRD definition for this is in the Rook examples, which makes getting the Toolbox up and running very easy before connecting to Rook:

# kubectl create -f toolbox.yaml
# kubectl -n rook-ceph exec -it $(kubectl -n rook-ceph get pod -l "app=rook-ceph-tools" -o jsonpath='{.items[0].metadata.name}') bash

The usual Ceph commands are now available. With ceph status, you can check the status of the cluster; ceph osd status shows how the OSDs are currently getting on; and ceph df checks how much space you still have in the cluster. This part of the setup is therefore not specific to Rook.

Conclusions

Rook in Kubernetes provides a quick and easy way to get Ceph up and running and use it for container workloads. Unlike OpenStack, Kubernetes is not multiclient-capable, so the "one big Ceph for all" approach is far more difficult to implement than with OpenStack. For this reason, admins tend to roll out many individual Kubernetes instances instead of one large one. Rook is ideal for exactly this scenario, because it relieves the admin of a large part of the work: maintaining the Ceph cluster.

Rook version 1.x [5] is now available and is considered mature for deployment in production environments. Moreover, Rook is now an official Cloud Native Computing Foundation (CNCF) project; thus, it is safe to assume that many more practical features will be added in the future.

Infos