(from Redundant Array of Inexpensive Nodes, by analogy with RAID)

A high availability network attached storage (NAS) technology developed at Caltech under a NASA-funded grant.

RAIN uses commercial off-the-shelf hardware and load balancing software to provide a server farm for data storage and transmission.

In a sense, the original Napster was a peer-to-peer RAIN.

SOURCE: "RAIN Delivers Better Failover", Internet Week, June 25, 2001