diff --git a/doc/src/docbkx/common/config-drive.xml b/doc/src/docbkx/common/config-drive.xml
index ee01c0d591..5f2053af81 100644
--- a/doc/src/docbkx/common/config-drive.xml
+++ b/doc/src/docbkx/common/config-drive.xml
@@ -30,7 +30,12 @@
                         >#1165174</link>). Make sure you install this program on each compute host
                     before attempting to use config drive, or an instance will not boot
                     properly.</para>
-            </note></para>
+            </note>
+            <note><para>
+            If you use Xen with a config drive, disable the agent through the
+            <literal>xenapi_disable_agent</literal> configuration parameter.
+            </para></note>
+            </para>
     </simplesect>
     <simplesect>
         <title>Enabling the config drive</title>
diff --git a/doc/src/docbkx/openstack-config/compute-configure-backing-storage.xml b/doc/src/docbkx/openstack-config/compute-configure-backing-storage.xml
new file mode 100644
index 0000000000..502fc009e7
--- /dev/null
+++ b/doc/src/docbkx/openstack-config/compute-configure-backing-storage.xml
@@ -0,0 +1,33 @@
+<section xml:id="configuring-backing-storage"
+         xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xmlns:ns5="http://www.w3.org/1999/xhtml"
+         xmlns:ns4="http://www.w3.org/2000/svg"
+         xmlns:ns3="http://www.w3.org/1998/Math/MathML"
+         xmlns:ns="http://docbook.org/ns/docbook">
+  <title>Configuring Compute Backing Storage</title>
+  <para>Backing Storage is the storage used to provide
+  the expanded operating system image, and any ephemeral storage.
+  Inside the virtual machine, this is normally presented as two
+  virtual hard disks (eg /dev/vda and /dev/vdb respectively).
+  However, inside OpenStack, this can be derived from one of three
+  methods: LVM, QCOW or RAW, chosen using the
+  <literal>libvirt_images_type</literal> option in <literal>nova.conf</literal>
+  on the compute node.</para>
+  <para>QCOW is the default backing store. It uses a copy-on-write philosophy to
+  delay allocation of storage until it is actually needed. This means that the
+  space required for the backing of an image can be significantly less on the real
+  disk than what seems available in the virtual machine operating system.
+  </para>
+  <para>RAW creates files without any sort of file formatting, effectively creating
+   files with the plain binary one would normally see on a real disks. This can
+   increase performance, but means that the entire size of the virtual disk will be
+   reserved on the physical disk.
+  </para>
+  <para>Local <link xlink:href="http://http//en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)">LVM volumes</link>
+  can also be used.
+  Set <literal>libvirt_images_volume_group=nova_local</literal> where <literal>nova_local</literal> is the name
+  of the LVM group you have created.
+  </para>
+  </section>