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8-Node Clustering Coming in Windows .NET Enterprise Server

Microsoft will support eight-node failover clusters in Windows .NET Enterprise Server.

The decision came months after the Beta 3 release of the Windows .NET Server family editions back in November, when Microsoft announced that only four-node clusters would be supported in Windows .NET Enterprise Server, while eight-node failover clusters would be reserved for Windows .NET Datacenter Server customers.

A Microsoft spokesman told ENT that customer demand led to the change. "Making eight-node clustering exclusive to Datacenter Server does not fit within our focus of scalability and reliability [for Datacenter Server]," the spokesman said.

"Customers see a value in clustering and would like to more completely exploit that capability on smaller [four-processor] servers, which do not qualify for the Datacenter Server [which can only be purchased on eight-processor capable machines]," the spokesman said.

Market demand for greater than two-node clusters has been slow to develop. All demand for Microsoft failover clustering has pretty much been satisfied by two-node clustering up until now.

Microsoft first introduced its Microsoft Cluster Services (MSCS), or "Wolfpack", in the operating system in 1997 with the rollout of Windows NT Server 4.0, Enterprise Edition. The two-node limit inherent in the initial version carried through to Windows 2000 Advanced Server, released in February 2000. When Windows 2000 Datacenter Server launched in September 2000, it ratcheted up the capability to four nodes.

However, some customers ENT spoke with at the time who had scenarios for four-node clustering, suffered from sticker shock when they realized how much more expensive Windows 2000 Datacenter Server was than Windows 2000 Advanced Server.

For a loose comparison, on fairly recent audited benchmarks, HP listed a cost of about $20,000 for Windows 2000 Advanced Server running on eight servers, while IBM listed an operating system cost of about $440,000 for four servers running Datacenter Server.

At the Beta 3 release, Microsoft seemed inclined to reserve the more extensive clustering support as a value-add for Datacenter Server, with Enterprise Server (the follow-on product to Windows 2000 Advanced Server) maxing out at four nodes and Datacenter scaling to eight nodes. However, that has obviously changed.

For the record, IBM tried to capitalize on the two-node limitation before the Windows 2000 launch. At TechEd 99, IBM introduced a technology code-named "Cornhusker," which included eight-node failover using the Microsoft's MSCS APIs. The project never picked up momentum and faded from view after being repurposed as part of an IBM Storage Area Network solution.

The market may be more ripe for larger clusters today. Users are already accustomed to the concept of greater than two-node failover scenarios from Windows 2000 Datacenter Server. One consultant familiar with the technology reported substantial customer interest in ganging together four Exchange servers using Datacenter Server in organizations where Exchange uptime was becoming critical.

Documentation on Microsoft's Web site confirms Exchange deployments as one scenario, and mentions disaster recovery as another reason for the expanded capability. "This change was made to allow increased flexibility for deployments: particularly for geographically dispersed cluster configurations, and to support N+I configurations (N active with I spare). N+I will be particularly important for supporting larger Microsoft Exchange Server deployments using Windows .NET Server into the future," Microsoft's Web site says.

Along with eight-node support, Microsoft is building other features into MSCS that help with disaster recovery scenarios in Windows .NET Enterprise Server and Windows .NET Datacenter Server.

With its premium editions of Windows .NET Servers, Microsoft will support new cluster topologies that end the previous dependence on shared disk that made multi-site configurations difficult without third-party software.

"Majority Node Set [a new quorum mechanism with no shared disks] makes it easier to build and configure multi-site, geographically dispersed clusters," Microsoft maintains.

Additionally, Microsoft is adding the ability to use Cluster Administration from a remote management station to create server clusters, change configurations or remove servers from a cluster, all without reboots or a need for distribution media.

About the Author

Scott Bekker is editor in chief of Redmond Channel Partner magazine.

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