Improvements in Performance and Scalability in Exchange 2003

Improving performance and scalability has always been an important design goal for the Exchange product development team. The first Exchange product, Microsoft® Exchange Server 4.0, was designed to replace MS Mail for PC Networks. MS Mail could host no more than 500 mailboxes per post office. Most organizations, however, required a more enterprise-ready messaging platform. The information store in Exchange Server 4.0 and Microsoft Exchange Server 5.0, in contrast, could hold up to 16 GB of data and more than 500 mailboxes.

Storage capacity was further increased in Microsoft Exchange Server 5.5. Exchange Server 5.5 Enterprise Edition featured an unlimited Exchange information store. Now organizations could place any number of mailboxes on a single server, and Exchange databases could quickly grow to enormous sizes of several hundred GB. With its large database sizes, however, the messaging system was difficult to maintain. Although the number of mailboxes that could be contained within the Exchange store was theoretically unlimited, 1,000 mailboxes per server was the approximate practical limit.

Increasing the practical number of mailboxes per server was a major design goal for Microsoft Exchange 2000 Server. Exchange 2000 Server featured support for multiple storage groups and could hold up to 20 mailbox and public folder databases. When mailboxes were distributed over a number of mailbox stores, servers could host 2,000 or more mailboxes. The individual databases nevertheless remained manageable.

Exchange 2003 improves upon Exchange 2000 in the areas of performance, scalability, and security. Exchange 2003 continues to support multiple storage groups and messaging databases, features an additional Recovery Storage Group, and supports the Volume Shadow Copy service of Windows Server™ 2003. Exchange 2003 uses improved caching algorithms so that directory lookups can be completed more efficiently, resulting in a 60 percent reduction of Microsoft Active Directory® directory service queries compared with Exchange 2000. Virtual memory management is improved also, and the propagation of link state information between servers is optimized to reduce network traffic. Also noteworthy is the high level of virus and spam protection that you can achieve by using Exchange 2003. Upgrading to Exchange 2003 from previous versions of Exchange, especially Exchange Server 5.5, offers clear incentives.