This report describes an experimental disk block server implemented for the RSX-11M Operating System using DECnet. The block server allows user programs on one system to access files on a disk physically located on a different system. The actual interface is at the level of physical blocks and IO transfers. Results of basic performance measurements are given, and explained in terms of major components. Performance predictions are made for servers of this type supporting more complex workloads.

A fixed-space page replacement algorithm is presented. A variant of FIFO management using a secondary FIFO buffer, this algorithm provides a family of performance curves lying between FIFO and LRU. The implementation is simple, requires no periodic scanning, and uses no special hardware support. Simulations are used to determine the performance of the algorithm for several memory reference traces. Both the fault rates and overhead cost are examined.

Digital Equipment Corporation has recently developed a new PDP-11 operating system called IAS—Interactive Application System. Since the system was to be significantly different from existing PDP-11 systems, customers and DEC field personnel had little information about the kinds of load it would handle or what level of performance could be expected. The work reported in this paper had the objective of producing such information prior to the release of the product. The major goal was to produce a set of guidelines indicating the kinds of loads that could be handled within limits of acceptable performance by various IAS configurations. The guidelines had to be in terms understandable to salesmen and customers. At the same time they had to be based on technically sound performance measurements that could be precisely explained and repeated.