The primary hardware difference between Exchange 2003 and Exchange 2007 is the move from a 32-bit platform (Exchange 2003) to a 64-bit platform (Exchange 2007). Exchange 2007 will only be supported in production environments when it is running on an x64-based version of Windows Server 2003.

The change from a 32-bit platform to a 64-bit platform requires a new approach to choosing server hardware for Exchange, especially processor and memory.

We recommend that you choose a processor that will work with both 32-bit and x64-based versions of Windows 2003. The following server processors support both 32-bit and x64-based versions of Windows 2003, thereby supporting Exchange 2003 deployments today, and Exchange 2007 deployments tomorrow:

• AMD Opteron
  
• Intel Xeon with EM64 Technology
  

  Note:
  The third-party Web site information in this topic is provided to help you find the technical information you need. The URLs are subject to change without notice.

Each of these vendors also ships x64-capable desktop processors which can also run x64-based versions of Windows 2003 (for example, AMD Athlon64 and Intel Pentium D with EM64T) but for the sake of simplicity, this article will concentrate on processors designed for server deployments.

It is important to note that the Intel Itanium (IA64) processor will not work with Windows 2003 x64-based versions, and thus it will not work for Exchange 2007 deployments. Exchange 2007 is designed to run only on x64-capable processors such as those listed above; Exchange 2007 will not run on Itanium based systems.

Regardless of which server processor you select, it is necessary to have the server product pass the Designed for Windows test suite to ensure Microsoft support. Servers listed on the Windows Server Catalog meet these criteria. If your server is not listed, check with your vendor to see if either the "Designed for Windows" logo testing is in progress, or the server has passed the testing and is pending a Web site update.

The TechNet x64 Newsgroup is a good place to get more information about moving from 32-bit Windows to 64-bit Windows.

The short answer is yes. Extensive testing on dual-core processors has shown that Exchange benefits from dual-core processor technology. The performance benefit for Exchange from dual-core technology depends upon the specific processor used. The findings from Exchange 2003 dual-core testing have been summarized in Microsoft Knowledge Base article 827281, CPU and memory scalability for Exchange Server 2003 and for Exchange 2000 Server. Additionally, the performance benefit of specific dual-core implementations can be seen by comparing the MMB3 results of a 4-processor, single-core based server to a 2-processor, dual-core based server. These results have been published at the Performance Benchmarks for Computers Running Exchange Server 2003 Web site.

Today, dual-core processors are an attractive option for Exchange 2003 and Exchange 2007 servers based on price and performance. Please ask your server vendor about dual-core benefits for Exchange, specific to a given hardware architecture.

Exchange 2007 enables much better memory utilization than Exchange 2003 due to its 64-bit architecture. Because of the virtual address space limitations of a 32-bit platform, Exchange 2003 is limited to using 4 GB or less of physical memory. In contrast, Exchange 2007 running on Windows 2003 x64-based versions will efficiently utilize upwards of 16 GB of memory and beyond (Mailbox role). This change needs to be factored in when putting together server hardware for Exchange 2003 that can be migrated to Exchange 2007 server roles. The following factors should be considered:

• Server Maximum Memory Configuration   Different server architectures have different memory limits. We recommend that you check the following technical specifications of the server to determine the criteria that affect the maximum memory configuration to ensure that memory upgrades from Exchange 2003 to Exchange 2007 can be accommodated economically:
  
  • Memory Speed   Some server architectures require slower memory to scale up the memory to ten's of gigabytes in a given server (for example, maximum server memory is limited to 16 GB with PC3200 or 32 GB using PC2700). You should check with the manufacturer to ensure that the memory configuration target for both Exchange 2003 and Exchange 2007 are compatible in terms of speed.
    
  • Memory Module Size   What is the largest memory module size the server will support? Generally, the larger the memory module, the more expensive it is; 2x1 GB DDR SDRAM memory modules generally cost much less than 1x2 GB DDR SDRAM memory modules. When planning for an Exchange 2003 server, make sure the maximum memory module size allows you to meet your target memory requirements for Exchange 2007. It may make sense to spend more money and purchase denser memory modules for an Exchange 2003 deployment to ensure that the memory requirements for Exchange 2007 can be met in the future.
    
  • Total Number of Memory Slots   How many memory modules will a given server support? The total number of slots multiplied by the maximum memory module size will provide the maximum memory configuration for the server. Keep in mind that memory modules must sometimes be installed in pairs.
    
• Memory upgrade path from Exchange 2003 to Exchange 2007   After you understand the memory requirements of a given server, you can design the optimal memory configurations for Exchange 2003 while simultaneously designing an upgrade path to Exchange 2007.
  Example   In this example, let's say you wanted to purchase a server for Exchange 2003 (Backend/Mailbox role). The Exchange 2003 best practice for maximum memory is 4 GB, but you want to ensure you will have the capability to upgrade to 16 GB when you deploy Exchange 2007. You analyze the manufacturer technical specs and find the following:
  
  • Memory Speed   Specifications say 16 GB is possible with PC3200 but 32 GB requires PC2700.
    
  • Memory Module Size   Specifications say 4 GB is max memory module size.
    
  • Total Number of Memory Slots   Specifications say there are eight total memory slots (8*4 GB = 32 GB Max memory configuration). Specification also states memory must be added in pairs.
    

With this information, it is determined that 2 GB PC2700 or 2 GB PC3200 memory modules will provide a good memory configuration for Exchange 2003 (2x2 GB). Moreover, the server can be upgraded to 16 GB (8x2 GB) to significantly reduce the I/O for an Exchange 2007 Mailbox Server in the future. If 1 GB memory modules were chosen for the Exchange 2003 configuration, the server could not be upgraded to 16 GB without having to throw out the 1 GB memory modules and replace them with 2 GB memory modules. One caveat with this planning method is that some servers experience a performance improvement when more memory slots are filled, while others experience a reduction in performance. Check with your hardware vendor to understand this effect for a given server architecture.

The following chart can be used to assist in purchasing server hardware destined to be used for both Exchange 2003 and Exchange 2007 server roles. The goal of this chart is to provide an upper bound of viable processor/memory configurations for Exchange 2007. This is not a statement of "Best Practice" but a simple guide for purchasing server hardware for Exchange 2003 that can be used for Exchange 2007. The effectiveness in terms of hardware price and performance for each Exchange 2007 server role is still being ascertained.

Example   In choosing a server platform for an Exchange 2003 Mailbox/BE that is destined to be reused as an Exchange 2007 Mailbox server, it would make sense to choose a server that has a maximum physical memory capacity of 32 GB for a scaled up deployment (~4000 mailboxes per server). It would be unfortunate to choose a server that had a maximum physical memory capacity of 8 GB for this role and then not be able to effectively reduce I/O with 16 GB or 32 GB of memory when transitioned to Exchange 2007 service. The maximum configurations outlined above for Exchange 2007 are not "optimal" configurations, but the current maximums the Exchange Product Group is developing against.

I hope I have offered some insight on how to choose server hardware for Exchange 2003 that can be used for Exchange 2007 deployments tomorrow. With effective planning and an understanding of the basic processor and memory requirements of both versions, the investments made today in current Exchange 2003 infrastructures can continue to be leveraged with Exchange 2007.