Optimizing an Exchange Server 2007 Environment : Analyzing Capacity and Performance

Examining Exchange Server 2007 Performance Improvements

Before delving into ways to tweak Exchange Server 2007 performance, it is important to have an understanding of the performance improvements that have been made since its predecessor, Exchange Server 2003. Although some of these performance improvements are more noticeable than others, Exchange Server 2007 has been designed to scale into the enterprise and beyond.

Architectural Improvements

One of the largest and most apparent changes in Exchange 2007 is the move to a 64-bit architecture. This provides Exchange 2007 with new opportunities for scalability and performance that were not available with 32-bit code. By eliminating the legacy limitation of a 3-GB memory space, the Exchange engine is no longer as limited in how much information it can cache. This means that Exchange is no longer as limited by disk input/output (I/O) performance. When configured with sufficient memory, Exchange 2007 can reduce its disk I/O requirements by as much as 75%. This allows administrators to be much more efficient in their use of disks.

The 64-bit architecture of Exchange 2007 also allowed Microsoft to raise the limits on the number of databases that could be hosted by a single Exchange server. Whereas Exchange 2003 was only capable of a total of 20 databases (spread out across four storage groups), Exchange 2007 is able to host as many as 50 databases (spread out across 50 storage groups). This again offers administrators greater flexibility in how they design their Exchange 2007 servers, which can result in increased performance if it is designed correctly.

Database Engine Improvements

Microsoft has continued to make great strides with the JET database. JET is the database used by Exchange 2007, as well as in previous versions of Exchange, to store mailbox data and public folder data. In the new 64-bit version of JET offered by Exchange 2007, the JET engine is able to take advantage of the lift in restrictions on memory space and it allows JET to allocate significantly more cache for the Exchange store. This means that users have access to more cache and this greatly increases the likelihood that data requested by a user is already in memory and doesn’t have to be read from disk. This results in quicker response times for the end users. Similarly, the database page size in Exchange 2007 has been increased from 4KB to 8KB. Although this might not seem significant, the result is that more messages are able to fit into a single database page and, as a result, the Exchange server needs only one I/O operation rather than two to retrieve the message. This also helps to significantly reduce the overall I/O requirements of the Exchange 2007 server.

Transport Pipeline Improvements

The transport pipeline refers to the collection of server roles as well as various queues, components, and connections within Exchange that work together to transport messages to the message categorizer in the Hub Transport server. The job of this categorizer is to deliver mail to the appropriate location within the Exchange environment. This process has been greatly improved in Exchange 2007 and is able to handle significantly more messages than earlier versions of Exchange.

Analyzing Capacity and Performance

Capacity and performance analysis for an Exchange Server 2007 environment requires a well-established understanding of the business and messaging needs of the organization and a well-documented outline of the organization’s expectations of its messaging environment. The capacity of an Exchange environment is directly dependent on the expected level of performance. It is important to understand exactly what it is you are expecting from the system in terms of storage per user, level of responsiveness of the server, and room for anticipated expansion. When armed with these concepts, you can more accurately determine what your current capacity is.

The first step in capacity analysis is to grasp an understanding of these concepts and define performance expectations. This can be done by establishing policies and service level agreements (SLAs). It is in these policies and SLAs that an administrator can outline acceptable performance thresholds and more accurately gauge the capacity needs of Exchange Server 2007. These thresholds can also be used to accurately establish performance baselines from which to analyze the requirements against available resources.

To help develop the policies and SLAs, use questionnaires, interviews, business objectives, and the like along with performance measurements via the Performance Monitor, Exchange Best Practices Analyzer, or third-party analysis tools. This allows you to combine realistic expectations with concrete data to see where you are relative to where you want to be.

Establishing Baselines

The importance of establishing meaningful baselines of the messaging environment cannot be underscored enough. Baselines are particularly important in the sense that they are the measurable tools that can be used to balance what is required of Exchange Server 2007 with what resources are needed to fulfill those requirements. Achieving this balance can be made simpler if an administrator consults performance metrics, such as industry-standard benchmarks. By starting with an accurate baseline of system performance, you can quickly and easily test changes in the environment to see if they have made things better or worse. Accurate baselines are also very helpful when troubleshooting problems and you can quickly determine which subsystems are not performing the way they normally do. A clear baseline allows you to determine whether a server that “seems slow” really is slower than the way it usually runs.

To establish an accurate baseline of Exchange Server 2007, a number of tools can help an administrator in this process. These tools are discussed in detail in the following sections. Some of these capacity analysis tools are built in to Windows Server 2003, and others are built in to Exchange Server 2007. Many third-party tools and utilities are also available for the careful measurement of Exchange Server 2007 capacity requirements and performance analysis.

Using the Exchange Best Practices Analyzer Tool

The Exchange Best Practices Analyzer (ExBPA) is a utility provided by Microsoft that analyzes an Exchange server’s configuration and informs administrators on possible configuration changes that can be made to improve performance or mitigate problems. More specifically, ExBPA can be used to perform a health check, a health and performance check, a connectivity test, and a baseline test. This tool, which was a download in previous versions of Exchange, is now a built-in tool. To access the Best Practices Analyzer, perform the following steps:

1.	Launch Exchange Management Console.
2.	If the left pane, scroll down and select Toolbox.
3.	In the action pane, click Open Tool from under the Best Practices Analyzer option.
4.	When the Best Practices Analyzer tool launches, check the Check for Updates on Startup check box, and click Check for Updates Now.
5.	If there are updates available, click Download the Latest Updates.
6.	After being updated, the tool closes, and you have to click it again.
7.	Choose Go to Welcome Screen.
8.	Click Select Options for a New Scan.
9.	Type the name of your closest global catalog, and click Connect to the Active Directory Server.
10.	Enter a label for this scan, choose the systems you want to scan, choose Health Check, and click Start Scanning.
11.	When the tool has finished, click View a Report of This Best Practices Scan to display an output similar to the one shown in Figure 1. Figure 1. Viewing ExBPA reports.

When viewing the report, an administrator is able to see any critical issues, nondefault settings, or recent changes to the system. This quickly identifies configuration settings that might be detrimental to the overall performance of the system. Be sure to always update the Best Practices Analyzer before running it because Microsoft is constantly adding new information to this tool.

The Informational Items tab offers a convenient and consolidated view of information that is typically captured in Exchange documentation. Take advantage of this view when tracking the configuration of your Exchange 2007 servers.

Using the LoadSim Tool

Loadsim is a “stress test” tool written by Microsoft to allow an administrator to simulate the load of multiple users against an Exchange server. This can be especially helpful in validating the performance and capacity of a system by testing it prior to attaching live users to it. LoadSim can be downloaded from the Microsoft website at http://www.microsoft.com/downloads/details.aspx?familyid=92EB2EDC-3433-47CA-A5F8-0483C7DDEA85&displaylang=en.

To simulate a load against an Exchange server, follow these steps:

While the load simulation is running, you can monitor the performance counters on the Exchange 2007 server and see how the system is handling the load. This allows you to validate your design in terms of how the server is configured versus the anticipated user load.

Don’t forget to delete the user and distribution list objects from Active Directory when you are finished with your testing.

Planning for Growth

One of the easiest ways to maintain the performance of an Exchange 2007 server is to plan ahead for the growth of the environment. Too many administrators have a tendency to build an Exchange infrastructure that meets the storage and performance requirements of today but that fails to account for the growth of the company.

Typically, when designing an Exchange 2007 infrastructure, you should try to look ahead roughly 3 years to predict the size to which the company will grow. This is a good time to talk to groups such as Human Resources and Finance to see the rate at which the company has grown historically. This will give you a good idea of how many employees would be utilizing the Exchange environment in 3 years. This process should also uncover specific expansion plans for the company. For example, if the company were going to grow from 10,000 employees to 13,000 employees in 3 years, you would naturally consider that a 30% growth and would allow for an extra 30% capacity on servers. However, if the case were that 2,000 of those employees would be in a new facility in Japan that was going to be online in 2 years, it would really be a 10% growth across the enterprise and potentially a very large increase in capacity needs in Asia or perhaps an entirely new Exchange site in Japan.

Understanding these types of growth allow you to more easily plan for capacity growth and understand how the increase in user load will affect the performance of your Exchange 2007 servers in various sites.

The other thing to consider when planning for growth is the increases in usage of the Exchange environment. It is common to see companies increase the storage limits for users without changing the number of users on a server. There are also third-party technologies that might be in your 3-year plan that will leverage Exchange 2007 as a storage or transport. Voice mail system, Structured Query Language (SQL), or Oracle implementations could quickly increase the loads placed on your Exchange 2007 servers.

The reason it is important to predict, as best you can, these anticipated growths is because it is often easier to account for these needs at the time of the Exchange 2007 design. Most companies are using storage area networks (SANs) or network attached storage (NAS) for the mailbox stores in Exchange. Although these systems do have the ability to resize their LUNs to offer additional storage, this is a very time-consuming process and it directly impacts the users on the server. Similarly, because these are usually shared storage devices, there is likely not enough spare capacity on the shelf or device to allocate more space to the Exchange servers. This results in the SAN or NAS administrator having to allocate additional space in a nonoptimal way, which can affect the performance of all the applications that attach to the NAS or SAN.