Planning Processor Configurations

Microsoft Exchange Server 2007 will reach end of support on April 11, 2017. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.

Applies to: Exchange Server 2007, Exchange Server 2007 SP1, Exchange Server 2007 SP2, Exchange Server 2007 SP3

There are many factors to consider when selecting hardware for use by Microsoft Exchange Server 2007. Three of the most critical factors to consider are choice of processor, amount of memory, and selection of storage. This topic provides guidelines for processor configurations that provide good performance and a strong platform for Exchange Server. For detailed guidance and recommended configurations for memory, see Planning Memory Configurations. For detailed guidance and recommended storage configurations, see Planning Storage Configurations.

Selecting the Appropriate Processor

For production environments, you must choose a processor that will work with the x64-based version of Windows Server:

• The release to manufacturing (RTM) version of Microsoft Exchange Server 2007 is only supported in production environments when the x64 version of Exchange 2007 is installed on a computer with x64-compatible processors that is running the Windows Server 2003 x64 Edition operating system.

• Microsoft Exchange Server 2007 Service Pack 1 (SP1) is only supported in production environments when the x64 version of Exchange 2007 is installed on a computer with x64-compatible processors that is running the Windows Server 2003 x64 Edition or the 64-bit editions of the Windows Server 2008 operating system.

You can select processors from Intel that support Intel Extended Memory 64 Technology or processors from AMD that support AMD64. For more information about these processor options, see the Intel 64 Architecture Web site at https://developer.intel.com/technology/intel64/index.htm, or see the AMD Opteron Processor Family Web site at https://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_8825,00.htm.

Itanium processors cannot be used and are not supported for Exchange 2007. Exchange 2007 is designed to run only on x64-capable processors such as those listed previously, and it will not run on Itanium-based systems.

Regardless of which processor you choose, the server product must have the Designed for Windows logo to be supported. For more information, see Windows Hardware Certification. To ensure support, you must select a server that is listed in the Windows Server Catalog. If your server is not listed, you should verify with the hardware vendor that testing is in progress.

Multi-Core Processors

Extensive testing on dual-core processors has shown that Exchange Server benefits significantly when it uses multi-core processor technology. The performance benefit for Exchange Server from dual-core technology depends upon the specific processor used. The findings from Exchange Server 2003 dual-core testing are summarized in Microsoft Knowledge Base article 827281, CPU and memory scalability for Exchange Server 2003 and for Exchange 2000 Server.

Today, multi-core processors are an attractive option for Exchange 2007 based on price and performance. We recommend that you ask your hardware vendor about dual-core benefits for Exchange Server for your specific hardware platform.

Recommended Processor Configurations

You can use the following table to assist you in purchasing server hardware for Exchange 2007. This table provides minimum requirements, recommended requirements, and recommended maximum configurations for Exchange 2007.

The following describes the minimum requirements, recommended requirements, and recommended maximum configurations:

• Minimum   This is the minimum processor and memory configuration suitable for specific server roles. The minimum hardware requirements must be met to receive support from Microsoft Product Support Services.

• Recommended   This is the recommended processor and memory configuration for specific server roles. Recommended is defined as the best configuration based on price and performance. The recommended configuration also provides a balance between processor and memory capacity. The goal is to match the memory configuration to the processor configuration so the system will effectively use the processors without becoming bottlenecked on memory and vice versa.

• Maximum   This is the maximum recommended processor and memory configuration for specific server roles. Maximum is defined as the upper bound of viable processor and memory configurations based on price and performance. The recommended maximum configuration is a guideline. It is not a support criterion, and it does not take into account the resource requirements of third-party applications that might access or be installed on the server. The recommended maximum configuration may change over time based on price changes and technology advancements.

Processor configurations for Exchange 2007 server roles

Edge Transport Server Role

The Edge Transport server role is extremely efficient in design and thus requires moderate processing power. In addition, organizations requiring fault tolerance will deploy multiple Edge Transport servers to provide redundancy. The recommended configuration of 2 x processor cores assumes a fault-tolerant deployment. Large organizations, with a substantial volume of inbound and outbound messages, will be able to use servers with 4 x processor cores to reduce the aggregate Edge Transport server count. Processor utilization is based on several factors such as: message rate, average message size, number of enabled transport agents, antivirus configuration, and third-party applications.

Hub Transport Server Role

The recommended configuration for the Hub Transport server role is 4 x processor cores in organizations where Hub Transport servers are deployed with several Mailbox servers and thousands of mailboxes. 8 x processor core servers can be efficiently used when the Hub Transport server is configured to use antivirus and anti-spam. Either 1 x or 2 x processor core configurations can be considered for organizations where there are not enough mailboxes or insufficient message traffic to warrant using a 4 x processor core configuration. Processor utilization is based on several factors such as message rate, average message size, number of enabled transport agents, antivirus configuration, and third-party applications.

Client Access Server Role

Exchange 2007 architecture has moved most of the client-specific functions from the Mailbox server to the Client Access server. In Exchange 2007, messages are converted on the Client Access server when they are accessed by a non-MAPI client (for example, POP3 and IMAP4 clients). In addition, rendering for Microsoft Outlook Web Access is performed on the Client Access server, as opposed to the Microsoft Exchange Information Store service in previous versions of Exchange Server. These architectural changes allow the Client Access server to offload significant processing from the Mailbox server and enable the Client Access server to effectively utilize 4 x processor cores. Servers with either 1 x or 2 x processor cores can be utilized for Client Access servers in organizations where there are not enough mailboxes or insufficient non-MAPI client traffic to warrant using 4 x processor core servers.

Unified Messaging Server Role

The recommended configuration for the Unified Messaging server role is 4 x processor cores. Multiple cores are used on the Unified Messaging server for several architectural functions such as .wav to Microsoft Windows Media Audio (WMA) conversions for voice mail messages. Servers with either 1 x or 2 x processor cores can be used for Unified Messaging servers in organizations where there are not enough mailboxes or insufficient Unified Messaging server activity to warrant using 4 x processor core servers.

Mailbox Server Role

The recommended configuration for the Mailbox server role is based predominantly on mailbox count and user profile. A 4 x processor core server provides a good balance between price and performance, and should be able to host several thousand mailboxes. Sizing for the Mailbox server requires an understanding of the average client user profile. This profile can be collected using the Microsoft Exchange Server Profile Analyzer or by using third-party tools. For more information, see the Microsoft Exchange Server Profile Analyzer Web site. The following table lists generic and common knowledge worker profiles for Microsoft Outlook clients.

Knowledge worker profiles for Outlook users

There are several factors to consider when sizing Mailbox servers other than the user types listed earlier. These include Mailbox servers that use Exchange 2007 features such as local continuous replication (LCR), and Mailbox servers that are accessed by Microsoft Forefront Security for Exchange Server, third-party applications, mobile devices, and online (versus Cached Exchange Mode) Outlook clients. Sizing used primarily for budgeting purposes can be accomplished by assuming that 1,000 active average profile mailboxes will require a 1 x processor core (for example, a 4,000-mailbox server with an average usage profile requires 4 x processor cores). A heavy usage profile requires more processor cycles than an average profile, thus for planning purposes use 750 active heavy profile mailboxes per processor core. Therefore, a 6,000-mailbox server with a heavy profile requires a 8 x processor core server. The maximum number of processor cores efficiently used by the Mailbox server role is 12. Deploying mailboxes on servers with more than 12 cores will not provide significant scalability improvements.

Processor Recommendations for Local Continuous Replication

In an LCR environment, both the active copy and passive copy of LCR-enabled storage groups are on the same server. In this environment, there is additional processing overhead generated from the Microsoft Exchange Replication service copying and replaying logs to the passive copy of the database. This additional processing overhead is approximately 20 percent and should be considered when sizing Mailbox servers that have one or more storage groups enabled for LCR.

Multiple Server Roles

The guidance for a computer with multiple server roles installed is similar to the Mailbox server role. To accommodate the Client Access and Hub Transport server roles on the same server as the Mailbox server role, reduce the 1,000 mailboxes per core calculation based on the average client profile by 20 percent (800 mailboxes per core) when performing sizing. The maximum recommended processor core configuration is listed at 6 x processor cores for the multiple server roles configuration to indirectly provide guidance on the maximum number of users that should be hosted on a multiple role server. Neither cluster continuous replication (CCR) nor single copy clusters (SCC) support hosting the Hub Transport or Client Access server roles in a failover cluster, so the multiple role server is non-clustered. It is a good idea to cluster Mailbox servers that host thousands of mailboxes to make sure that server maintenance or failures do not have a significant impact on uptime or availability. For this reason, the recommended maximum processor core configuration for the multiple server roles configuration is listed at four. Although this configuration can use up to 12 processor cores, we do not recommend this configuration due to availability concerns.

For More Information

For more information about an issue that occurs when you try to install Exchange 2007 on a computer that is running 25 or more processor cores, see Microsoft Knowledge Base article 981539, Installation of Exchange Server 2007 fails on a multiprocessor server.