BIB-VERSION:: CS-TR-v2.0
           ID:: STAN//CSL-TR-97-729
        ENTRY:: July 16, 1997
 ORGANIZATION:: Stanford University, Computer Systems Laboratory
        TITLE:: Remote Memory Access in Workstation Clusters
         TYPE:: Technical Report
       AUTHOR:: Verghese, Ben
       AUTHOR:: Rosenblum, Mendel
         DATE:: july 1997
        PAGES:: 22
     ABSTRACT:: Efficient sharing of memory resources in a cluster of
                workstations has the promise of greatly improving the
                performance and cost-effectiveness of the cluster when
                running large memory- intensive jobs. A point of interest is
                the hardware support required for good memory sharing
                performance. We evaluate the performance of two models: the
                software-only model that runs on a traditional distributed
                system configuration, and requires support from the operating
                system to access remote memory; and the hardware-intensive
                model that uses a specialized network interface to extend the
                memory system to allow direct access to remote memory. Using
                SimOS, we do a fair comparison of the performance of the two
                memory-sharing models for a set of interesting compute-server
                workloads. We find that the software-only model, with current
                remote page-fault latencies, does not provide acceptable
                memory-sharing performance. The hardware shared-memory system
                is able to provide stable performance across a range of
                latencies. If the remote page-fault latency can be reduced to
                100 microseconds, the performance of the software- only model
                becomes acceptable for many, though not all, workloads.
                Considering the interconnection bandwidth required to sustain
                the software-only page-level memory sharing, our experiments
                show that a gigabit network is necessary for good
                performance.
        NOTES:: [Adminitrivia V1/Prg/19970716]
          END:: STAN//CSL-TR-97-729