Server Operating System

The Windows 2000 generation of server products marked a significant milestone in Microsoft's quest for true enterprise-scale products. With the prior NT 4.0 generation, there were still general-purpose business solutions that were beyond the reach of Microsoft's operating systems. The operating system also constrained the performance of SQL Server, preventing it from contending as the most powerful relational database. Nonetheless, SQL Server 7 was able to deliver excellent marks for cost effectiveness and manageability, even if it left a certain low percentage of potential users untouched.

With Windows 2000 and the concurrent growth in hardware to accompany it, Windows can scale to meet virtually any business need. It runs on much more powerful servers than NT 4.0, addresses more memory, and scales through symmetric multiprocessing and clustering.

Windows 2000 offers three levels of the server operating system. Windows 2000 Server is for department and small business use. Windows 2000 Advanced Server is designed for higher availability, while Windows 2000 Datacenter Server meets the most demanding needs for large-scale computing. The latter versions of Windows 2000 break the former limit on addressable memory of 4 GB of RAM.

The directory component of Windows 2000 and Windows 2003 is Active Directory, and it is a key for scalability. Prior versions of Windows could only store 3,000 to 40,000 objects, creating a barrier for large organizations and certainly for portals. Active Directory is highly scalable, robust, and secure. Tests indicate the performance degradation with Active Directory (caused by replication among the Active Directory instances) begins at about one million users in a domain. The global catalog replication overhead creates a practical limitation of approximately five domains with one million users in each domain. Therefore a configuration of five Active Directory domains per forest equates to a practical limit of five million accounts.

Microsoft provides the excellent article "Active Directory in the Outward- facing Role" at www.microsoft.com/downloads/details.aspx?displaylang=en&familyid=e95b2d36-d746-4f57-ae79-e2adba31ec95, but you will find it easier to search for it by name . This document explains how to use AD as a single sign-on architecture for your portal, using a tight consistency model of directory replication.