Computer cluster – Wikipedia, the free encyclopedia.

A computer cluster is a group of linked computers, working together closely thus in many respects forming a single computer. The components of a cluster are commonly, but not always, connected to each other through fast local area networks. Clusters are usually deployed to improve performance and availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability.^[1]

And now I will put together clusters for high availability and load balancing.  This is where VMs come in handy.   I think I  prefer loosely coupled clusters, clusters where individual nodes are separated on different power grids.

It’s always nice to have a succinct definition handy to stay focused.