CLOUDSTACK-4799: rewrite section based on the patch since the doc Migrate to rst format
diff --git a/rtd/source/concepts.rst b/rtd/source/concepts.rst
index c8aa36f..5db3653 100644
--- a/rtd/source/concepts.rst
+++ b/rtd/source/concepts.rst
@@ -15,7 +15,7 @@
Concepts and Terminology
-========================
+========================Primary storage is associated with a cluster
What is Apache CloudStack?
--------------------------
@@ -410,8 +410,9 @@
About Primary Storage
~~~~~~~~~~~~~~~~~~~~~
-Primary storage is associated with a cluster or (in KVM and VMware) a
-zone, and it stores the disk volumes for all the VMs running on hosts.
+Primary storage is associated with a cluster, and it stores
+virtual disks for all the VMs running on hosts in that cluster.
+On KVM and VMware, you can provision primary storage on a per-zone basis.
You can add multiple primary storage servers to a cluster or zone. At
least one is required. It is typically located close to the hosts for
