Server and site consolidation have been on my mind a lot as the release of Exchange Server 2003 gets closer. Exchange Server 5.5 administrators might be wondering whether Exchange 2003 can help them reduce their site and server counts; Exchange 2000 Server administrators might wonder whether another upgrade would mean any real consolidation benefit. This week, I want to lay out a consolidation scenario that might help illustrate the answers to these questions.
Server consolidation means moving workload to fewer, more powerful servers. Site consolidation reduces the number of physical sites that host servers (presumably equipping the sites with better connectivity and more powerful servers). Both methods offer potentially large savings, which is part of what makes them so attractive. Even though the initial cost of buying new servers or relocating facilities might be high, the cost savings in reduced overhead, easier management, and better recoverability can more than pay for the consolidation. Microsoft and a variety of IT consulting firms have conclusively demonstrated that server or site consolidation involving Windows 2000 and Windows NT file servers is often too good a deal to pass up—-but what about consolidation involving Exchange servers? The answer, as usual, is "It depends."
First let's examine a large Exchange 5.5 organization. Because Exchange 5.5 sites function as both message-routing and security boundaries, most Exchange 5.5 organizations tend to have at least several sites to accomodate multiple routing groups--large organizations typically have 40 to 100 sites. That's a lot of overhead, both in terms of replication bandwidth and administration time.
Consider what the organization might look like if it migrates to Exchange 2000. Exchange 2000 supports routing and administrative groups, so the organization can consolidate sites into a few administrative groups with routing groups added in to break the organization up into islands of connectivity. Because Exchange 2000 Enterprise Server supports multiple large databases per machine and takes full advantage of multiprocessor servers, the organization can easily consolidate servers to host 1500 to 2000 users per machine (although a good disaster-recovery plan had better be in place). Sites that ran an Exchange 5.5 server just to support a few local users can be removed, and users can access a front-end server running Outlook Web Access (OWA) 2000, with little loss of functionality.
Now what about moving on to Exchange 2003? From a server-consolidation standpoint, Exchange 2003 and Exchange 2000 are largely identical, although Exchange 2003 offers a few benefits. The Information Store (IS) in Exchange 2003 is more efficient at allocating RAM, the added support for four- or eight-node N+1 clusters means that you can consolidate servers onto clusters instead of onto standalone servers, and the new /USERVA switch provides better scalability on systems with more than 1GB of RAM. The true benefit, however, lies in Exchange 2003's site-consolidation-friendly features. Sites that maintain local servers for Messaging API (MAPI) clients who have resisted moving to OWA can use remote procedure calls (RPCs) over HTTP to give clients full Outlook functionality from a centrally managed set of servers. Improvements in MAPI bandwidth utilization (not to mention OWA's compression capabilities when teamed with compatible browsers) help make site consolidation even more compelling because more efficient bandwidth usage translates into getting more clients to the server across one connection. When used together, Outlook 2003 (running in cached mode) and Exchange 2003 are tuned to optimize bandwidth usage and request patterns, so deploying them together further improves performance and scalability.
There's a lot more to the Exchange 2003 consolidation story, including several back-end features that can let you build larger mailbox servers without raising the degree of risk that a server failure will affect users. Next week, I'll take a look at some of these features and explain what you can do with them. In the meantime, think about how consolidation might benefit you. Let me know whether you think it makes sense in your environment.