Hi.
Heartbeat is usually a private network between the nodes, used to send data
about which nodes are alive. You'll want a low latency network for this. Google
for clusters and heartbeat and you'll find lots of information I'm sure.
Clusters can be used as High-Availiblity where server B is ind
>From my experience with clustering that is when the connection between parts
>of the clusters are lost and they can't agree on which one is supposed to keep
>serving the data. The most common way around it afaik is to have a priority
>and heartbeat between the nodes and allow them to kill each
