pvecm.adoc: improve document structure

pvecm.adoc

@@ -58,27 +58,29 @@ Requirements
 
 * All nodes must be in the same network as corosync uses IP Multicast
  to communicate between nodes (also see
- http://www.corosync.org[Corosync Cluster Engine]). NOTE: Some
- switches do not support IP multicast by default and must be manually
- enabled first.
+ http://www.corosync.org[Corosync Cluster Engine]). Corosync uses UDP
+ ports 5404and 5405 for cluster communication.
++
+NOTE: Some switches do not support IP multicast by default and must be
+manually enabled first.
 
 * Date and time have to be synchronized.
 
-* SSH tunnel on port 22 between nodes is used.
+* SSH tunnel on TCP port 22 between nodes is used. 
 
-* If you are interested in High Availability too, for reliable quorum
-  you must have at least 3 nodes (all nodes should have the same
-  version).
+* If you are interested in High Availability, you need to have at
+  least three nodes for reliable quorum. All nodes should have the
+  same version.
 
 * We recommend a dedicated NIC for the cluster traffic, especially if
   you use shared storage.
 
 NOTE: It is not possible to mix Proxmox VE 3.x and earlier with
-Proxmox VE 4.0 cluster.
+Proxmox VE 4.0 cluster nodes.
 
 
-Cluster Setup
--------------
+Preparing Nodes
+---------------
 
 First, install {PVE} on all nodes. Make sure that each node is
 installed with the final hostname and IP configuration. Changing the
@@ -89,7 +91,7 @@ need to login via 'ssh'.
 
 
 Create the Cluster
-~~~~~~~~~~~~~~~~~~
+------------------
 
 Login via 'ssh' to the first Proxmox VE node. Use a unique name for
 your cluster. This name cannot be changed later.
@@ -102,7 +104,7 @@ To check the state of your cluster use:
 
 
 Adding Nodes to the Cluster
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
+---------------------------
 
 Login via 'ssh' to the node you want to add.
 
@@ -111,15 +113,16 @@ Login via 'ssh' to the node you want to add.
 For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
 
 CAUTION: A new node cannot hold any VM´s, because you would get
-conflicts about identical VM IDs. To workaround, use vzdump to backup
-and to restore to a different VMID after adding the node to the
-cluster.
+conflicts about identical VM IDs. Also, all existing configuration is
+overwritten when you join a new node to the cluster. To workaround,
+use vzdump to backup and restore to a different VMID after adding
+the node to the cluster.
 
 To check the state of cluster:
 
  # pvecm status
 
-.Check Cluster Status
+.Cluster status after adding 4 nodes
 ----
 hp2# pvecm status
 Quorum information
@@ -167,7 +170,7 @@ Membership information
 
 
 Remove a Cluster Node
-~~~~~~~~~~~~~~~~~~~~~
+---------------------
 
 CAUTION: Read carefully the procedure before proceeding, as it could
 not be what you want or need.