The hardware that you select for your Exchange deployment has the greatest effect on performance. Because of the large number of variables that affect performance, it is difficult to predict the effects on performance of any particular hardware component. The following sections provide general information about what components affect Exchange Server 2003 performance, including processors, memory, network, and storage.
Processor Performance
The processor usage on a server should maintain a load of about 60 percent during peak working hours. This percentage level allows room for periods of extreme load. If the processor usage is consistently greater than 75 percent, processor performance is considered a bottleneck.
There are several factors by which the CPU in a server affects performance. These include:
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The processor clock speed, measured in megahertz (MHz) or gigahertz (GHz).
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The number of processors.
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The type of processor.
For performance, selecting the fastest processor yields the best results. However, budget cost dictates most companies' choices.
Besides the clock speed, the technology used in a processor can affect performance. For example, some processors use Hyper-Threading Technology, which enables a single processor to act as two virtual processors. Such processors typically incorporate advanced cache management and increased bus speed features.
Exchange can fully use multiple processors and, in many cases, using servers with more processors improves performance. However, the relationship between the number of processors and performance is complex. If the server has too many processors, the overhead associated with context switching can be greater than the benefit from the additional processors. The optimum number of processors is partly determined by the role that a server plays. For example, a back-end mailbox server hosting many MAPI connections may make efficient use of an eight-processor computer. By contrast, a server used to host Microsoft Outlook® Web Access users makes better use of a four-processor computer.
For information about how different processors perform, see Scaling Exchange Server 2003.
Memory Performance
Exchange services typically consume no more than 3 gigabytes (GB) of physical memory. After you add operating system requirements and antivirus, backup, and management software, the total physical memory that is used can approach 4 GB. On servers that are dedicated to Exchange, you do not need more than 4 GB of memory.
The biggest individual consumer of memory in Exchange Server 2003 is the Store.exe process, which manages mailboxes and public information storage
Besides the Store.exe process, other processes that consume memory (and may affect performance) include:
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Inetinfo.exe Process that handles Internet protocols
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Emsmta.exe Microsoft Exchange MTA Stacks service
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Mad.exe Microsoft Exchange System Attendant
For more information about memory optimization, see Tuning Exchange Server 2003 Performance.
Network Performance
Much of the network interface subsystem is tuned automatically. Server-based network adapters are capable of detecting the type and level of traffic passing through the network interface, and they self-tune to reflect this information. Beyond making sure that you have the latest device driver on the server, there is not much to do here.
For mailbox servers, a full duplex 100 megabits per second (Mbps) network connection is typically sufficient. However, if you plan to back up and restore across the network, consider using gigabit Ethernet (1,000 Mbps or 1 gigabits per second [Gbps]).
Generally, the greatest bottleneck in a front-end and back-end server configuration is the network that separates the two sets of servers. Front-end servers can consume a 100 Mbps LAN connection. Therefore, consider multiple switched fast Ethernet networks of gigabit Ethernet connections.
Performance-related issues may be because your hardware, firmware, or software drivers are not designed to work in your configuration. For more information, see the Products Designed for Microsoft Windows Web site.
Storage Performance
As storage requirements increase and companies consolidate servers, you must balance the cost, availability, and performance when you design a storage system. Take time to invest in good storage design before you implement it; unlike processors and memory, which you can scale while the network is active, storage redesign requires network downtime to implement. Tuning your Exchange storage becomes the most critical component.
There are many storage solutions available, including locally attached storage and storage area networks (SANs). The storage requirement of an Exchange server depends on the role of the server. For example, a back-end server would benefit from a SAN because of the large amount of critical data the server must store and present. SANs are specialized storage hardware that incorporates redundant array of inexpensive disks (RAID) technology to ensure high availability and performance. In contrast, a front-end server is more processor intensive, and it does not require an advanced storage solution.
With the advancements in data capacity, adding a larger capacity hard disk drive does not solve performance issues related to increased user loads. You must consider the ability of each hard disk drive to respond sufficiently to various user loads. This ability can be measured by analyzing your current user loads. Chapter 2 discusses a method you can use to analyze your current database usage. With this data, you can estimate your storage requirements.
For more information about storage strategy, see the Exchange Server 2003 High Availability Guide.