Kubernetes volume plugins evolution from FlexVolume to CSI

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Back in the days, when Kubernetes was still young (v1.0.0 or so), there were volume plugins. They were required to connect persistent data storage volumes to Kubernetes. Their number was relatively low at that time. The GCE PD, Ceph, AWS EBS, and some others were among the first storage providers.

Usually, they were bundled with Kubernetes. That’s why they were called “in-tree plugins”. However, many developers have felt that the range of available plugins was quite limited. So they have created their own solutions, integrated them into the Kubernetes core via patches, compiled their own versions of Kubernetes and installed them on servers. But over time, Kubernetes developers have realized that you cannot solve the problem by giving “a man a fish” — you have to teach him “to fish”. So they decided to include a “fishing rod” in version 1.2.0 for those who need it…

Please, read the rest here.