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Microsoft officials say only that four-server clustering will be available after Windows 2000 Datacenter Server ships, which will probably be late in the first quarter or in the second quarter of 2000. Datacenter Server will support only two-node failover with some load balancing. Why the delay in more advanced clustering? Ed Muth, Microsoft group product manager for Win2000 servers, says it's difficult to ensure recovery from a failure once more than two machines that fail over to each other and support load balancing are strapped together.

Glenn Bonner, CIO of Mirage Resorts Inc., looks forward to more robust clustering from Microsoft. Mirage has two-server clusters for systems on which high availability is crucial, such as its hotel system. For most clusters, Bonner has one idle computer. "We're very interested in adding load balancing," he says.

Hardware vendors are pushing ahead with plans to differentiate their upcoming cluster offerings. Dell Computer, which will demonstrate a four-server cluster running a beta of Win2000 in May, last week licensed ClusterX from NuView Inc. ClusterX helps users install, configure, and manage clusters. Dell is also working with NuView on tools for efficiently distributing workloads among servers and allowing administrators to build partitions among servers for load-balancing.

Both Compaq and IBM say they are working with Microsoft to formalize four-node cluster plans within the next few months. Compaq recently also debuted Intelligent Cluster Administrator and Insight Manager XE-Cluster Monitor for simplifying administration and enhancing operations in a mixed-configuration environment. Hewlett-Packard said last week that it certified Giganet Inc.'s Cluster LAN for managing clusters of NetServers.

IBM sources say it will debut an eight-server configuration that uses an extension to Cluster Server for workload balancing beyond four nodes. It will be based on RS/6000 and S/390 technology. Microsoft argues that four-node clustering is sufficient for most applications; Muth says about 98% of the market consists of clusters of four nodes or fewer. Rob Enderle of Giga Information Group says he doesn't see a problem with a four-node limit, "because there's a question as to whether anyone would trust an eight-node cluster [or larger]."

Jim Shelton, IS director of wholesale distributor Global Petroleum Corp. in Waltham, Mass., doesn't even trust his cluster of two Unisys servers running Cluster Server. He says all the events required for failover never pull together. "I have no strong warm fuzzies that it will work in a crisis," says Shelton.

Microsoft says that while Windows 2000's kernel can support up to 16 servers in a "shared-nothing" cluster, designing tests to certify hardware vendors' many interconnection technologies is daunting. "We support SCSI, switched SCSI, Fibre Channel," and more, says Muth. "Testing is complex." Case in point: Dell says it will license technology from a small company that develops high-speed system interconnects for its cluster platform.

Interim Solution?
For users aiming mainly at high availability, clustering several nodes is just one solution. James Gruener, managing director of Aberdeen Group, says fault-tolerant hardware and high-availability services can help fill the void in the interim.

Stratus Computer Inc. plans to have a fault-tolerant Win2000 system for general business use as soon as the operating system ships. It will cost no more than two commodity Windows NT servers. "Customers can buy two or more servers for a cluster, and deal with failover times and incompatible software," says Steve Kiely, Stratus' president and CEO, "or buy our single server to run existing apps."