It is only in the last five years that researchers have begun to use disk-based search techniques on a large scale. The primary examples of its use come from symbolic algebra and from artificial intelligence. In the field of parallel search, disk-based search has been forced on researchers because the historical growth in the amount of RAM per CPU core has now stopped. Indeed, the current trend toward multi-core CPUs now threatens to take us backwards. This article makes an original contribution to the design of disk-based parallel search algorithms. It presents a survey of disk-based techniques side-by-side, for the first time. This allows researchers to choose from a menu of techniques, and also to create new hybrid algorithms from the building blocks presented here.