Windows 2000 Datacenter Server, as a superset of Win2K Advanced Server, offers several enhancements and features to meet large enterprises' requirements. These features include Physical Address Extension (PAE) support, Winsock Direct, the Process Control tool, hardware partitioning, and the Windows Datacenter Program.

PAE, which enables efficient access to memory above 4GB on 32-bit Intel-based systems, is a component of the Enterprise Memory Architecture (EMA). EMA lets applications efficiently access vast amounts of RAM and adds dramatically to the performance of Win2K AS and Datacenter systems. Such systems exhibit very little disk paging, so they provide applications with the fastest possible environment because the OS and applications can exist entirely in RAM. PAE permits Win2K AS systems to access as much as 8GB of RAM; Datacenter systems can access as much as 64GB.

Winsock Direct is a Winsock extension that lets standard TCP/IP-based Winsock applications (e.g., Internet Explorer—IE) run unmodified on high-speed System Area Networks. SANs are similar to LANs but are physically secure and offer higher bandwidth and lower latency than traditional LANs. SAN hardware's built-in reliability features also virtually guarantee that packets will route correctly and efficiently. Before Winsock Direct, most SAN application programming required an understanding of proprietary transport technology because most SANs don't use TCP/IP. In Datacenter, though, Winsock Direct makes SAN access as transparent and speedy as standard LAN access—without requiring a TCP/IP installation.

Process Control is a Datacenter system service that includes a Microsoft Management Console (MMC)-based tool and command-line utility that lets you assign specific resources to particular applications. The feature works with a Datacenter-specific kernel object, called a job object, that you can use to collect one or more server processes into one named unit. Job objects have numerous capabilities, and you can use Process Control to create rules that expose these capabilities. For example, you might create a rule that prevents an application from using too much RAM or processor time. You can use Process Control for a variety of related tasks (e.g., assigning scheduling priority to processes or process groups, enforcing processor and memory limits for processes).

Datacenter's hardware-partitioning feature lets you run multiple copies of Datacenter on the same physical server. Datacenter is the first Microsoft OS to offer this capability. (Microsoft SQL Server 2000 offers a similar feature that lets you install more than one copy of SQL Server on a system.)

One of Datacenter's most important features isn't even part of the OS. To offer customers an end-to-end solution comprising hardware, software, and support, Microsoft has joined with its first-tier hardware partners to create the Windows Datacenter Program, which requires that Datacenter be preloaded onto servers from one of these partners only. In other words, you can't purchase Datacenter separately and install it on home-brew hardware. Also, Datacenter will be bundled only with hardware that passes Microsoft's rigorous testing and certification process, giving customers a guaranteed solution with one entry point for support and service.

Microsoft has also created the Windows Hardware Quality Labs (WHQL) and Hardware Compatibility Test (HCT) so that these vendors can ensure that their products work with Datacenter and other Win2K versions. Microsoft guarantees that hardware products that pass the HCT will work with Datacenter. The company will place these products on the Datacenter Hardware Compatibility List (HCL), an exclusive subset of the Win2K HCL. To qualify systems for the Datacenter HCL, PC makers must ensure that the systems' hardware drivers, kernel-level software, virus software, disk- and tape-management software, backup software, and the like are Datacenter-certified; this requirement should result in highly dependable Datacenter systems. Vendors must maintain these Datacenter-compatible systems for 18 months longer than the life of the current Datacenter version. Vendors must also offer a variety of services (e.g., full installation of the OS and all drivers, an evaluation of Datacenter in the customer's environment, onsite service through the vendor or a third party) to Datacenter customers. Datacenter systems must guarantee a minimum uptime of 99.9 percent, with clustered systems offering even higher uptimes.

The fact that Microsoft won't offer Datacenter through retail channels also affects licensing. Qualified PC makers will offer three basic licensing options: support for as many as 8 processors, 16 processors, or 32 processors. (Customers can upgrade to 16- and 32-processor licenses as needed.) To qualify for a Datacenter license, a server doesn't need to ship with eight processors, but it must support at least that many out of the box. Datacenter doesn't ship with any Client Access Licenses (CALs); customers must purchase CALs separately.

PC makers can also offer Datacenter with a subscription license, which customers can update yearly and which will give customers access to annual version releases, supplements, and Datacenter-specific service packs. Customers who purchase this type of license can opt to discontinue the subscription; customers who don't purchase the license immediately can subscribe to it later.