Load Testing Exchange 2000

If you're getting ready to implement Microsoft Exchange 2000 Server,you've probably been thinking about load testing—an important step in evaluating Exchange 2000's effectiveness in your environment. You can use load testing to appraise basic Exchange system functionality (i.e., whether email goes where it's supposed to), but load testing's usefulness doesn't end there. Exchange 2000 setup involves populating Windows 2000's Active Directory (AD), but the process is fairly quick and populating the environment and driving a load in Exchange are easier than building other database-driven solutions. Therefore, load testing Exchange is a good way to determine the abilities of a new piece of hardware or to test a network design. (You can use Exchange load testing to demonstrate a proof of concept—for example, to show the performance of a distributed Web architecture that uses front-end servers for client connection points and back-end servers for mailbox stores.) Using this method, you can have new hardware running in a matter of days.

As Web Table 1 shows, a variety of tools are available for testing Exchange, depending on the type of clients you want to represent and the protocols you want to test. (For more information about how to view this table, see "More on the Web," page 61.) One of the most well-known tools is the Microsoft Exchange Load Simulator (LoadSim), which works well with Messaging API (MAPI) clients such as Microsoft Outlook. LoadSim 2000 is the most recent version of the tool and can provide excellent data about your Exchange 2000 servers. (For information about using earlier versions of LoadSim with Exchange Server 5.5, see Greg Todd's four-part series about LoadSim 5.0, beginning with "Understanding and Using LoadSim 5.0: Part 1," January 1998, InstantDoc ID 3429.) You can use Win2K's Performance Monitor to capture and analyze performance data, then adjust your Exchange Server configuration depending on what you discover.

LoadSim 2000
LoadSim lets you select the number of Outlook clients that you want to simulate against specific Exchange Servers. You can choose from preselected load profiles, or you can create custom profiles. The tool includes a light, medium, and heavy profile. Earlier versions of the tool used the MAPI Messaging Benchmark (MMB) for the medium profile, but to simulate more realistic email usage, LoadSim 2000 uses the updated MMB2 for the default light-usage profile. Don't be fooled into thinking that MMB2 is lightweight, though. MMB2 adds significantly more client-generated load than MMB did—MMB2 is about seven times heavier than MMB.

The Microsoft Exchange 2000 Server Resource Kit contains LoadSim, but I recommend you use the most recent version: LoadSim 2000 build 4612, which you can download at http://www.microsoft.com/exchange/downloads/2000/loadsim.asp. The version that ships with the Exchange 2000 resource kit is substantially different from the downloadable version. Instead of creating mailboxes and distribution lists (DLs) in AD in one step, the resource kit version generates two files (i.e., a .csv and a .pkl file). You need to use the Exchange Migration Wizard to import the .pkl file, which is a packing list; this step populates AD. This extra step is unnecessary when you use the most recent LoadSim version. Also, the earlier version is based on the Exchange 5.5 hierarchy (i.e., site.org.com) and doesn't use the predefined MMB2 profile.

To run a custom profile, you can enable or disable specific actions (e.g., browse public folders), as Figure 1, page 60, shows. You can even throw huge attachments into the mix. This capability makes LoadSim quite easy to use and gives you a great deal of control. One word of caution, though: When you customize client tasks, you must specifically enable each task that you want the customized test to simulate. Any tasks that you don't enable manually won't show up in your test. This seemingly simple point can be easy to forget because enabling and customizing tasks involves several steps and dialog boxes. For ease of use, stick with MMB2 unless you have a specific reason to alter the client profile.

Installing LoadSim
The LoadSim installation folder contains a setup program so that you can install LoadSim on your client systems from one location. However, I simply copy the entire folder to the local hard disk of each client machine I want to use. The folder contains the core files loadsim.exe, loadout.dll, and lslog.exe, as well as 33 .msg files, which are the messages that LoadSim sends out during testing. Your client systems need to run Outlook 2000—LoadSim 2000 doesn't support Outlook 2002. If you plan to use the MMB2 load, you can use a maximum of 500 simulated users for each client machine of recent vintage (i.e., a Pentium 500MHz processor or better with at least 128MB of RAM). If you use a slower Pentium processor with 128MB of RAM, consider limiting the number of simulated users to 200. To guard against client bottlenecks, which will cause the Exchange servers to sit idle, set up one client machine with 100 or fewer simulated clients. When you analyze your test results, this client should show the same results as the others. If not, the client machines are overloaded and can't generate a complete load against the server.

Log on at each client as the Domain Administrator. Using this account is a LoadSim requirement, so be sure to run your tests in a laboratory AD forest only. You don't need to configure AD; LoadSim will create the necessary containers. On each client, create an Outlook profile (e.g., for the Administrator), then launch Outlook to ensure that the program is working and to register Outlook as the default client for email and contacts. This step is vital if LoadSim is to function properly. I usually enable autologon—something I'd never do with a production Domain Administrator account—to enable fully automated testing. For instructions about setting up autologon, see the Microsoft article "How to Enable Automatic Logon in Windows" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q310584).