Add README

README.md

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+zfs-operator
+=============
+
+![envtest](https://github.com/yuanying/zfs-operator/workflows/envtest/badge.svg)
+
+zfs-operator is a light-weight Kubernetes Operator that operates ZFS Dataset on Node (currently only ZVOL).
+
+Architecture
+------------
+
+zfs-operator manages zfs datasets using zfs cli, so this operator should be placed on each nodes.
+
+Concepts
+--------
+
+### Volume
+
+Volume is a representation of  ZVOL.
+
+```yaml
+apiVersion: zfs.unstable.cloud/v1alpha1
+kind: Volume
+metadata:
+  name: volume-sample
+spec:
+  nodeName: node01
+  volumeName: "tank/sample"
+  capacity:
+    storage: 5Gi
+  properties:
+    key: value
+```
+
+Installation
+------------
+
+zfs-operator runs within your Kubernetes cluster as a series of daemonset resources. It utilizes `CustomResourceDefinitions` to configure zfs datasets.
+
+It is deployed using regular YAML manifests, like any other application on Kubernetes.
+
+```bash
+$ kubectl kustomize "github.com/yuanying/zfs-operator.git/config/default?ref=master" | kubectl apply -f -
+```
+
+Usually, there are only a few nodes where you want to install zfs-operator to manage zfs dataset. This manifest assumes such cases. Please label your node where you want to install this operator like following.
+
+```bash
+$ kubectl label node ${ZFS_NODE} zfs.unstable.cloud/storage=
+```
+
+If zfs-operator is installed successfully, you can see some pods in zfs-operator-system namespace like this.
+
+```bash
+$ kubectl get pod -o wide
+NAME                          READY   STATUS    RESTARTS   AGE   IP            NODE            NOMINATED NODE   READINESS GATES
+zfs-operator-zfs-node-74wkf   2/2     Running   42         11d   10.244.1.10   ${ZFS_NODE}     <none>           <none>
+```