InformationWeek

ServerNet: Clustering's Core

By Logan Harbaugh

andem Computers' ServerNet is a high-speed interconnect technology developed to support server clustering. Clustering, used for years in the minicomputer and mainframe markets, achieves higher levels of reliability and greater total system capacity.

Clusters connect several systems together so that they act as one large system. To do this, the systems must be able to share the data in their memory, on their hard disks, and on other storage systems. Since servers today can have as much as 4 Gbytes of memory and several terabytes of storage, very-high-speed connections are necessary to allow transfers within reasonable periods of time.

Even relatively high-speed networking protocols such as Fast Ethernet and FDDI (100 Mbps) or ATM (155 Mbps or 650 Mbps) fall short when compared with the speed of transfers between blocks of memory within a system. ServerNet provides 2.8 Gbps of throughput, or 2,800 Mbps.

Another limitation of standard networking protocols is that there is a ceiling on the tota l bandwidth available to the network. This means that on a 100-Mbps network segment with eight systems, any system trying to communicate with the network might have only 12.5 Mbps of throughput available. ServerNet provides a switching fabric that gives each connection between two devices the same 2.8 Gbps of throughput.

Several vendors have announced that they will support ServerNet, including developers of both major network operating systems: Microsoft with its Wolfpack, and Novell with its Wolf Mountain clustering software for its IntranetWare platform.

Until recently, there was no competing technology. Fibre Channel has been adapted to the task of clustering. But ServerNet technology is proven, while Fibre Channel switching products are just now coming to market and are still slower than ServerNet.

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