nagy%bsndbg.hepnet@LBL.ARPA.UUCP (03/04/87)
>While studying the Guide to VAXclusters about dual-pathed disks (connected to >2 HSC's) I began to wonder how to achieve load-balancing between the 2 >HSC's if you use allocation-classes. >..... I once asked the developers about this and was told that it is not possible currently. VMS Development was considering providing automatic (another SYSGEN parameter?) HSC load balancing in the future. In point of fact, why bother? When the HSC70 was announced, Digital published some performance information indicating when one should make the move from an HSC50 to an HSC70. The result of staring at the graph was that an HSC50 has lots and lots of throughput. It seems to take a cluster of multiple 86xx (or 8550/8700/8800) class machines before the HSC50 begins to saturate. By then, such large clusters are already into multiple HSC pairs to support large disk farms anyway. If you only have a few 78x systems on your cluster, your HSC50s are perfectly capable of handling the load (i.e., one HSC50 can handle all your tape/disk I/O needs with no performance bottleneck).