"Kubernetes is not the only container orchestrator. There’s also Cloud Foundry, Mesos, Docker Swarm, and several others. Each of these container orchestrators needs to be able to run a variety of persistent workloads (such as a MySQL database or a Kafka cluster). Each of these persistent workloads needs to be able to use different types of backing storage.
With the range of container orchestrators and the range of backing storage types, a problem arises. Every storage type would have to write custom code to connect to each container orchestrator.
The solution to this is the CSI: the container storage interface."
Container Orchestrators (CO)