The commoditisation of hardware and operating system components will require high-end commercial system vendors to differentiate their next-generation products by other means. All indicators point to high-bandwidth, low-latency, highly-scalable system and device interconnects – or the big bus – will be that key differentiator. Fault-tolerant systems builder Tandem Computers Inc – now looking for 50% of its business to come from commercial decision support within two years – last week put its head out in front of the pack, unveiling an ambitious hardware-software big bus interconnect called ServerNet. Tandem, a champion of the massively parallel processing model that throws CPUs at problems, now says that it is simply not cost-effective to keep adding expensive processors and touts ServerNet as a System Area Network, or SAN, that enables any server component – CPU, storage or communications device – to interconnect directly without processor intervention. Instead of a processor on every data path, six-port, packet-switching routers implemented in an ASIC provide intelligent switching and wormhole routing with 300Mbps bandwidth per router (planned to double over time) and three microsecond message latency. Tandem says it means many of the large blocks of data required by text, image and video applications of the future will be retrieved through routers that will cost a few hundred bucks without having to pass through costly CPUs. ServerNet is an additional layer that logically and physically isolates processor buses from input-output buses (dispensing with memory-mapped input-output), and provides processor and bus interfaces for VME, PCI and other device interconnects. It’s the productisation of a three-year TNet – trusted network – development effort and will, the company claims, enable the creation of very large configurations of hybrid symmetric multiprocessing, clustered and parallel systems. Examples include a data mining system configured with thousands of processors providing throughput of hundreds of Gigabits per second; a phone company switching server festooned with communications devices and relatively few processors and disks or a video server with a large database, many communications devices but relatively few processors. ServerNet links connect processing nodes either within a cabinet over the backplane, or to other cabinets that can up to 100 feet off, over copper cable. Future implementations using serial fibre connections may extend the distance. Fault tolerance over the ServerNet bus is achieved by using duplicated connections in alliance with Tandem’s N+1 hardware topology.
