Add doc for rbd static pvc support

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

docs/static-pvc.md

@@ -0,0 +1,119 @@
+# Static PVC with ceph-csi
+
+- [Static PVC with ceph-csi](#static-pvc-with-ceph-csi)
+  - [RBD static PVC](#rbd-static-pvc)
+    - [Create RBD image](#create-rbd-image)
+    - [Create RBD static PV](#create-rbd-static-pv)
+    - [RBD Volume Attributes in PV](#rbd-volume-attributes-in-pv)
+    - [Create RBD static PVC](#create-rbd-static-pvc)
+
+This document outlines how to create static PV and static PVC from existing rbd image
+
+**warning** static PVC can be created, deleted, mounted and unmounted but
+currently ceph-csi doesn't support other operations like snapshot,clone,
+resize, etc for static PVC
+
+## RBD static PVC
+
+RBD images created manually can be mounted and unmounted to an app, below step
+shows how to create a rbd image, static PV, static PVC
+
+### Create RBD image
+
+If you already have a rbd image created and contains some data which you want
+to access by the application pod you can skip this step.
+
+Lets create a new rbd image in ceph cluster which we are going to use for
+static PVC
+
+```bash
+[$]rbd create static-image --size=1024 --pool=replicapool
+```
+
+### Create RBD static PV
+
+To create the rbd PV you need to know the `rbd image name`,`clusterID` and
+`pool` name in which the rbd image is created
+
+```yaml
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: fs-static-pv
+spec:
+  accessModes:
+  - ReadWriteOnce
+  capacity:
+    storage: 1Gi
+  csi:
+    driver: rbd.csi.ceph.com
+    fsType: ext4
+    nodeStageSecretRef:
+      # node stage secret name
+      name: csi-rbd-secret
+      # node stage secret namespace where above secret is created
+      namespace: default
+    volumeAttributes:
+      # Required options from storageclass parameters need to be added in volumeAttributes
+      "clusterID": "ba68226a-672f-4ba5-97bc-22840318b2ec"
+      "pool": "replicapool"
+      "staticVolume": "true"
+      #mounter: rbd-nbd
+    # volumeHandle should be same as rbd image name
+    volumeHandle: static-image
+  persistentVolumeReclaimPolicy: Retain
+  # The volumeMode can be either `Filesystem` or `Block` if you are creating Filesystem PVC it should be `Filesystem`, if you are creating Block PV you need to change it to `Block`
+  volumeMode: Filesystem
+```
+
+### RBD Volume Attributes in PV
+
+Below table explains the list of volume attributes can be set when creating a
+static RBD PV
+
+|  Attributes  |                                                                Description                                                                 | Required |
+| :----------: | :----------------------------------------------------------------------------------------------------------------------------------------: | :------: |
+|  clusterID   | The is used by the CSI plugin to uniquely identify and use a Ceph cluster (this is the key in configmap created duing ceph-csi deployment) |   Yes    |
+|     pool     |                                                The pool name in which rbd image is created                                                 |   Yes    |
+| staticVolume |                                      Value must be set to `true` to mount and unmount static rbd PVC                                       |   yes    |
+|   mounter    |                 If set to `rbd-nbd`, use `rbd-nbd` on nodes that have `rbd-nbd` and `nbd` kernel modules to map rbd images                 |    No    |
+
+**Note** ceph-csi does not supports rbd image deletion for static PV.
+`persistentVolumeReclaimPolicy` in PV spec must be set to `Retain` to avoid PV
+delete attempt in csi-provisioner.
+
+```bash
+[$] kubectl create -f fs-static-pv.yaml
+persistentvolume/fs-static-pv created
+```
+
+### Create RBD static PVC
+
+To create the rbd PVC you need to know the PV name which is created above
+
+```yaml
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: fs-static-pvc
+  namespace: default
+spec:
+  accessModes:
+  # ReadWriteMany is only supported for Block PVC
+  - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi
+  # The volumeMode can be either `Filesystem` or `Block` if you are creating Filesystem PVC it should be `Filesystem`, if you are creating Block PV you need to change it to `Block`
+  volumeMode: Filesystem
+  # volumeName should be same as PV name
+  volumeName: fs-static-pv
+```
+
+```bash
+[$] kubectl create -f fs-static-pvc.yaml
+persistentvolumeclaim/fs-static-pvc created
+```
+
+**Note** deleting PV and PVC doesnot deleted the backend rbd image, user need to
+manually delete the rbd image if required