|VAX clustering provides a way to couple processors and I/O devices in a "loose" way (so it's not symmetric or parallel multiprocessing). These nodes can share disks, processes, etc... The implementation was new in 1983, but became a hype in the late nineties. First, the node-to-node coupling used a high-speed serial interface, the CI (cluster interconnect), later on clustering became available on ethernet too (but obviously CI gave better performance). And not only processors could be sonnected this way, but also dedicated I/O controllers like the HSC-50, which was based on the PDP-11 architecture, and was able to provide hundreds of megabytes of disk/tape storage to clusters.
|The VAX-11/725 was a repackaged 11/730, that used an RC25 disk drive as storage. Unfortunately I've never seen one of these, so I cannot tell much about it...
DECnet phase IV: A This new revision of the DECnet protocols enabled connecting together more than a 1000 nodes.