add a backend type to the cluster crd

cluster/examples/kubernetes/rook-cluster.yaml

@@ -9,6 +9,8 @@ metadata:
   name: rook
   namespace: rook
 spec:
+  # the storage backend (only ceph is currently implemented)
+  backend: ceph
   # The path on the host where configuration files will be persisted. If not specified, a kubernetes emptyDir will be created (not recommended).
   # Important: if you reinstall the cluster, make sure you delete this directory from each host or else the mons will fail to start on the new cluster.
   # In Minikube, the '/data' directory is configured to persist across reboots. Use "/data/rook" in Minikube environment.

pkg/apis/rook.io/v1alpha1/types.go

@@ -45,6 +45,9 @@ type ClusterList struct {
 }
 
 type ClusterSpec struct {
+	// The type of backend for the cluster (only "ceph" is implemented)
+	Backend string `json:"backend"`
+
 	// The path on the host where config and data can be persisted.
 	DataDirHostPath string `json:"dataDirHostPath"`