Using the Model Editor to Fine-Tune
When you click Finish, you see the Model Editor screen, similar to the one that Figure 4 shows, displaying the global topology of the model that you created with the ModelWizard. You can use the links to the right of the diagram to perform actions such as adding new sites, editing usage profiles, and adding WAN links.
I recommend as a first step that you reconfigure the WAN links to match your proposed organization. To do so, double-click a WAN link in the diagram to edit that link. As you can see in Figure 5, you can set the uplink and downlink bandwidth for the link as well as its connection latency. To look at an individual site, double-click the image of the site in the diagram. When you do, you see a site-topology diagram similar to the one that Figure 6 shows. You can edit many different elements on this screen. Just as you double-clicked the WAN link in the previous diagram, double-click an element in this diagram to edit it.
The main items that you might want to customize in the individual sites are users and servers. By double-clicking a user, you can set the number of users in the site, what type of client they use to access their Exchange mailboxes, and how those users are connecting to the network. Editing user characteristics is a fairly simple process.
However, making changes to the servers within a site is a little trickier. When you double-click a server, you have the option to select a new hardware configuration for that server. The problem is that you're choosing a hardware configuration from a list. There's a good chance that your proposed server's configuration isn't on the list. Therefore, I recommend using Capacity Planner's Hardware Editor feature to define your hardware before modifying the site-topology diagram.
To use the Hardware Editor, click the Hardware Editor button at the lower left of the Model Editor screen. You'll see a screen similar to the one that Figure 7 shows: the Hardware Editor's Computer configurations screen, which contains a list of servers with specific processors and disk sizes. Click the New computer button to define a custom hardware configuration. The Hardware Editor lets you create a custom computer based on the processor and disks you select. The Device configurations option lets you create a custom CPU or disk. For CPUs, you can specify manufacturer, model, processor speed, physical processor count, L2 and L3 cache sizes, and bus speed. If you're defining a disk, you can specify storage size, interface type, seek time, rotational speed, and transfer rate. If you're defining a disk array, you can specify the disk type, disk count, and RAID level.
When you've defined all your hardware, you can select the new configuration for the server from the site-topology diagram by double-clicking a server and selecting the appropriate option from the Apply New Configuration menu on the bottom half of the screen, which Figure 8 shows. You can also rename the server by filling in the Server Name field; having actual server names in your model will make the diagrams easier to read.
Running the Simulation
Now that you've customized your model to match your proposed network, it's time to run a simulation by clicking the Run simulation button at the bottom of the Model Editor window's General Actions section. The time it takes the simulation to finish will vary depending on the complexity of your model. Figure 9 shows a summary of simulation results.
The Results Summary screen appears by default. Although the screen contains valuable information, you can get much more detail by using the options in the Simulation Results section-at the left. For example, you can obtain reports that show you how heavily individual servers or individual network links are being utilized. Other reports display the utilization of local network, SAN, and external connections. Problematic areas are flagged to call your attention to them. For example, if the volume of traffic exceeds what a connection can handle without exceeding the threshold you set, the connection is flagged as being a bottleneck. The Simulation Results screen also contains a page called Threshold Settings that lets you set threshold values for CPU utilization, disk utilization, the percentage of LAN and WAN bandwidth consumed, and overall latency. Unfortunately, Capacity Planner doesn't let you create a complete, formal report that you could export to another program, such as Microsoft Word. Another drawback with the tool is that it doesn't let you compare different configurations.
System Center Capacity Planner 2006 is an excellent tool for Exchange Server capacity planning. Keep in mind, though, that no tool is perfect. Capacity Planner can assist you in capacity planning, but it's up to you to interpret the results and to make intelligent decisions based on both the results and on what your own experience tells you.
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