Cluster vs. Farm

"Farm was generally used in load balancing scenarios and Clusters are generally used in high available(resilant) solutions.  In the web applications, a Farm is also a cluster because putting a switch infront of more than one machine and the DNS record for the web site is nothing but the IP address of the switch.  The switch depending on how  busy a server is routes the traffic to different machines.

Cluster, is usually a two machine node where one machine is active and other is passive (or active/active in true cluster environment).  But the processing is handled by only one machine and the other one is dormant.  When the active machine goes down, the other node takes over.

Farm is mainly used in web applications (stateless apps) where as clusters are used in database, server (windows service) type applications."