In recent years, Microsoft has taken a pummeling in the Web server business. At one time, IIS and Windows NT Server 4.0 was the most popular commercial Web server platform; today, Windows 2000 Server and Windows Server 2003 are fighting against a wave of free and inexpensive versions of the Linux operating system and Apache Web server software. Microsoft argues that such servers don’t come with the support that a multi-billion dollar company like Microsoft can provide; fans of Linux/Apache solutions say, "Who cares?" As a result, Microsoft has worked hard to provide a lower-cost version of Windows that’s optimized to be a high-speed Web server. Although lower-cost certainly doesn’t beat free, it does help close the gap and make potential buyers look at the additional features IIS offers, as well as the support Microsoft can provide. Microsoft’s lower-cost Web server solution is Windows Server 2003, Web Edition.

Windows Server 2003, Web Edition’s lower price doesn’t mean you’re getting a free lunch, though. For example, Web Edition lacks the other Windows Server 2003 editions’ Enterprise UDDI (Universal Data Definition Interface) services, which is an industry-standard way of publishing and locating information about XML Web services. And, even though Web Edition can be a member of an Active Directory domain, it can’t be a domain controller. Web Edition also lacks support for Microsoft Clustering, although it does include the NLB software that’s appropriate for creating Web farms.

Datacenter Edition builds on the feature set offered by Enterprise Edition and eliminates a few features that aren’t considered appropriate for a large enterprise data center. For example, Datacenter does not support the Internet Connection Firewall or Internet Connection Sharing, two features designed to make Windows an Internet gateway for network clients. Both features are, however, supported by Standard Edition and Enterprise Edition.

Datacenter Edition adds support for up to 64GB of server RAM and up to 32-way processor support. These features require a specialized Hardware Abstraction Layer (HAL), which is provided by the server hardware manufacturer. Datacenter Edition’s Cluster Service supports eight-way clusters, enabling you to build more complex failover clusters for mission-critical applications.

Windows Server 2003, Enterprise Edition fills many of the same roles as Standard Edition and adds features primarily geared toward improving reliability and scalability. Enterprise Edition supports a maximum of eight processors, which is double Standard Edition’s capability. Enterprise Edition also supports Address Windows Extensions (AWE), providing an extra gigabyte of memory to applications by reserving only 1GB for Windows, rather than Standard Edition’s 2GB/2GB split between the operating system and applications.

Enterprise Edition also supports Windows Clustering, allowing you to build failover clusters with two nodes. The Cluster Service allows you to create clustered file shares and clustered printers and supports clustered applications, such as SQL Server Enterprise Edition and Exchange Server Enterprise Edition. The Cluster Service even enables you to cluster applications that aren’t specifically designed for clustering, provided they meet certain criteria spelled out in the Windows online documentation.

Enterprise Edition can also host Microsoft Metadirectory Services (MMS), allowing large organizations to integrate multiple heterogeneous directories.

Standard Edition is the basic edition of Windows Server 2003 and is the one you’ll likely use the most. It’s suited to the broadest range of applications, particularly file serving, print serving, and low-demand application serving. Standard Edition supports a maximum of 4GB of server RAM, 4TB of disk space, and up to four processors.

Standard Edition supports the entire basic set of Windows Server 2003 features. It can act as a domain controller, public key infrastructure (PKI) server, and so forth. It does not offer clustering capabilities, aside from Network Load Balancing (NLB), which is included with all editions of Windows Server 2003.