A fault tolerant network server is described. This server has a pair of processing units, each processing unit has at least one CPU, system memory, an interface for a RAID system, at least one disk drive, a network interface, a cluster network interface, a power supply, and a case. The cases of both processing units are slideably mounted in a rack-mountable server case. The server also has a RAID system mounted in the server case and powered by two, redundant, power supplies and coupled to the processing units through isolators for blocking transactions when a processing unit has insufficient power or is being serviced.