"The cluster I'm going to create will be named cluster1.example.com, and it will have the IP address 192.168.0.102. The cluster IP 192.168.0.102 will always be bound to the cluster master, so even if you don't know which node is the master, you can use the cluster IP (or the hostname cluster1.example.com) to connect to the master using SSH.
"The Xen virtual machine (called an instance in Ganeti speak) will be named inst1.example.com with the IP address 192.168.0.105. inst1.example.com will be mirrored between the two physical nodes using DRBD - you can see this as a kind of network RAID1.
"As you see, node1.example.com will be the cluster master, i.e. the machine from which you can control and manage the cluster, and node2.example.com will be the primary node of inst1.example.com, i.e. inst1.example.com will run on node2.example.com (with all changes on inst1.example.com mirrored back to node1.example.com with DRBD) until you fail it over to node1.example.com (if you want to take down node2.example.com for maintenance, for example). This is an active-passive configuration."
