Add docs for RBD driver

.docs/user-guide/config.md

@@ -586,8 +586,9 @@ remote storage systems. Currently the following storage drivers are supported:
 [Isilon](./storage-providers.md#isilon) | isilon
 [ScaleIO](./storage-providers.md#scaleio) | scaleio
 [VirtualBox](./storage-providers.md#virtualbox) | virtualbox
-[EBS](./storage-providers.md#ebs) | ebs, ec2
-[EFS](./storage-providers.md#efs) | efs
+[EBS](./storage-providers.md#aws-ebs) | ebs, ec2
+[EFS](./storage-providers.md#aws-efs) | efs
+[RBD](./storage-providers.md#ceph-rbd) | rbd
 ..more coming|
 
 The `libstorage.server.libstorage.storage.driver` property can be used to
@@ -694,6 +695,7 @@ ScaleIO|Yes
 VirtualBox|Yes
 EBS|Yes
 EFS|No
+RBD|No
 
 #### Ignore Used Count
 By default accounting takes place during operations that are performed

.docs/user-guide/storage-providers.md

@@ -517,3 +517,89 @@ libstorage:
           region:         us-east-1
           tag:            test
 ```
+## Ceph RBD
+The Ceph RBD driver registers a driver named `rbd` with the `libStorage` driver
+manager and is used to connect and mount RADOS Block Devices from a Ceph
+cluster.
+
+### Requirements
+
+* The `ceph` and `rbd` binary executables must be installed on the host
+* The `rbd` kernel module must be installed
+* A `ceph.conf` file must be present in its default location
+  (`/etc/ceph/ceph.conf`)
+* The ceph `admin` key must be present in `/etc/ceph/`
+
+### Configuration
+The following is an example with all possible fields configured. For a running
+example see the `Examples` section.
+
+```yaml
+rbd:
+  defaultPool: rbd
+```
+
+#### Configuration Notes
+
+* The `defaultPool` parameter is optional, and defaults to "rbd". When set, all
+  volume requests that do not reference a specific pool will use the
+  `defaultPool` value as the destination storage pool.
+
+### Runtime behavior
+
+The Ceph RBD driver only works when the client and server are on the same node.
+There is no way for a centralized `libStorage` server to attach volumes to
+clients, therefore the `libStorage` server must be running on each node that
+wishes to mount RBD volumes.
+
+The RBD driver uses the format of `<pool>.<name>` for the volume ID. This allows
+for the use of multiple pools by the driver. During a volume create, if the
+volume ID is given as `<pool>.<name>`, a volume named *name* will be created in
+the *pool* storage pool. If no pool is referenced, the `defaultPool` will be
+used.
+
+When querying volumes, the driver will return all RBDs present in all pools in
+the cluster, prefixing each volume with the appropriate `<pool>.` value.
+
+All RBD creates are done using the default 4MB object size, and using the
+"layering" feature bit to ensure greatest compatibility with the kernel clients.
+
+### Activating the Driver
+To activate the Ceph RBD driver please follow the instructions for
+[activating storage drivers](./config.md#storage-drivers), using `rbd` as the
+driver name.
+
+### Troubleshooting
+
+* Make sure that `ceph` and `rbd` commands work without extra parameters for
+  ID, key, and monitors. All configuration must come from `ceph.conf`.
+* Check status of the ceph cluster with `ceph -s` command.
+
+### Examples
+
+Below is a full `config.yml` that works with RBD
+
+```yaml
+libstorage:
+  server:
+    services:
+      rbd:
+        driver: rbd
+        rbd:
+          defaultPool: rbd
+```
+
+### Caveats
+
+* Snapshot and copy functionality is not yet implemented
+* libStorage Server must be running on each host to mount/attach RBD volumes
+* There is not yet options for using non-admin cephx keys or changing RBD create
+  features
+* Volume pre-emption is not supported. Ceph does not provide a method to
+  forcefully detach a volume from a remote host -- only a host can attach and
+  detach volumes from itself.
+* RBD advisory locks are not yet in use. A volume is returned as "unavailable"
+  if it has a watcher other than the requesting client. Until advisory locks are
+  in place, it may be possible for a client to attach a volume that is already
+  attached to another node. Mounting and writing to such a volume could lead to
+  data corruption.