All server workstations run a remote memory server that handles requests for pageins, pageouts and informs the clients about the amount of its free memory. When a client wants to swap out a page it picks the most promising server. When a server runs out of memory, it informs its clients and stores some of its least recently used pages on its local disk. In this way, the servers act as a global LRU cache for the swap partitions of the cluster. In order to be able to recover from a single server crash, some form of redundancy must be used, so that lost pages can be reconstructed. We have implemented a new reliability technique, parity logging, that minimizes the memory and runtime overhead imposed to paging. Our performance results are very encouraging. Our test applications show that using the remote memory for paging results in a twofold improvement in execution time over an Ethernet interconnection network. Simulating faster networks we find that even higher performance improvements are realizable. More information on the project may be found at http://www.ics.forth.gr/proj/arch-vlsi/paging.html.
