Deploying Active Directory often necessitates a rather large hardware investment. One way to get a hardware estimate is to ask your hardware vendor, who will be more than happy to recommend that you spend your entire budget on new hardware—whether or not you actually need it. Another way is to sit with a pen and paper, add up all of Windows 2000’s system requirements, and then try to make a blind guess.

If neither of these options sounds very appealing, you’ll be glad to know that you now have a third option: Microsoft’s Active Directory Sizer utility. In this Drill Down, I’ll show you how you can use this handy utility to make an educated guess about the hardware needed for your organization to successfully deploy Active Directory.

What’s the Active Directory Sizer, and why do I need it?
The Active Directory Sizer is a free utility provided by Microsoft to help you figure out how much hardware you’ll need to successfully deploy Active Directory. Although you might think that you can just check Windows 2000 Server’s minimum system requirements and then pad them some and get by, you’re wrong. Sure, such a fudged system might work, but it won’t work efficiently.

Remember, Active Directory is a service that runs on top of Windows 2000, which is a very large service. As such, just maintaining Active Directory can overwhelm a Windows 2000 server that is at or near Windows 2000 Server’s minimum system requirements. The problem with judging Active Directory’s impact on Windows 2000 is that there is a huge number of variables to take into consideration.

The Active Directory Sizer presents these variables to you in a standard Windows 2000 Wizard format. By going through the wizard process and answering the questions, Sizer will give you a good idea of the optimal hardware configuration you need. Some of the things Sizer will advise you about include:

  • How many hard drives you’ll need to store the Active Directory database.
  • Optimal RAM configurations for your server.
  • Recommendations about network interface cards (NICs).
  • The number of domain controllers you’ll need.
  • The number of Global Catalog servers you’ll need.
  • What kind of processors your servers should run.

With this information in hand, you can purchase hardware that won’t collapse under the weight of your Active Directory tree but at the same time won’t pay for your hardware vendor’s winter home in Rio de Janeiro.

Obtaining and installing the Active Directory Sizer
You can obtain the Active Directory Sizer directly from Microsoft’s Active Directory Sizer Web site. Download Setup.exe to a temporary directory on your administrative workstation. It’s only 4 MB in size, so it won’t take very long to download. When the download completes, run Setup.exe from the temporary directory.

This will launch Sizer’s Setup wizard. This program works like every other Setup program you’ve ever worked with. Bypass the Welcome and License Agreement windows until you reach the Customer Information screen. If your administrative workstation is running Windows 2000 Professional, this screen will allow you to make Sizer available to other users who may use your workstation. It doesn’t matter which one you choose, although I prefer to choose Anyone, just in case I have to change login IDs on my workstation for some reason. Click Next to continue.

You’ll then see the Setup Type screen. Here, you can customize what features Setup will install as well as file locations. Click Complete to install everything to the default locations and click Next to continue. You should only choose Custom if you want to change the defaults.

After that, you’ll see a summary screen. Just click Install and let Setup go to work. It will copy all of the necessary files and configure your workstation as needed. When it’s done, you can begin using Sizer.

Running the Active Directory Sizer
To start Sizer, click Start | Programs | Active Directory Sizer| Active Directory Sizer. You’ll then see the Active Directory Sizer window appear. Although it may look like a Windows 2000 Microsoft Management Console (MMC), it’s not. The right pane initially just contains information about Sizer. After you run the Sizer Wizard, this screen will display Sizer’s recommendations. The left pane contains a tree that you’ll use after the Wizard runs to view the different recommended hardware configurations.

To start the Sizer Wizard, click New | File. You’ll then see the Active Directory Sizer Wizard appear, starting with the Introduction screen. On this screen, provide a name for your domain. You don’t have to provide the name for whatever you’ll ultimately name your domain. Merely enter a descriptive name so you can identify your results later if you save them. Click Next to continue.

You’ll then see the first of two User Accounts screen. On the first screen, you’ll tell Sizer how many users you’ll have in your Active Directory tree, how many users will concurrently be logged in at peak usage, and any additional attributes you’ll add for each user. By default, Sizer assumes that all of your users will be online at once. This isn’t realistic, so for our example, I’ve assumed that our test domain will have 250 users total, 85 percent of which (212) will be on at the same time. The Attributes field represents additional attributes you’ll define for each user object. The default of 25 is fine to leave here.

Click Next to go to the second User Accounts screen, shown in Figure A. On this screen, you’ll tell Sizer how many groups the average user will be a member of, how frequently passwords will expire, and the number of logons per hour that will occur at the server’s peak usage.

Figure A
Provide the Active Directory Sizer Wizard with information about your users’ activities.

Enter the values for the first two fields that represent average patterns on your network. You probably won’t have a clue what to put for the third question. Don’t panic. If you select the Estimate Logon Rates checkbox, the wizard will pop up a calculator that will automatically figure out the values to enter for you. Close the calculator and click Next to continue.

You’ll then see the first of two Computers And Other Objects screens. On the first screen, you’ll tell Sizer what kind of workstations your users will use to connect to Active Directory. In the Windows 2000 field, enter the number of workstations that are using either Windows 2000 Professional or Windows XP Professional. You’ll enter the number of Windows 9x and NT workstations that are connecting to Active Directory using Active Directory Client Extensions in the Other Computers field. The Other Objects field allows you to enter the number of groups, shares, printers, organizational units, and other objects you think you’ll have in your Active Directory tree. Click Next to continue.

You’ll then see the second Computers And Other Objects screen. On this screen, you’ll tell Sizer the maximum CPU utilization you want the servers on your network to have. You can also specify what CPU you’d like to use on your server. If you leave the CPU Type drop-down list boxes set to their default values of Autoselect, Sizer will recommend the best CPU type and speed combination for you. Click Next to continue.

The Administration screen, shown in Figure B, appears next. On this screen, you’ll use the drop-down list boxes to give Sizer some indication how frequently you’ll make changes to Active Directory objects. You can specify your workload in Daily, Weekly, or Yearly terms. After you select the interval, enter the objects you think you’ll add, delete, or change in the appropriate fields. Click Next to continue.

Figure B
Sizer must know how often you’ll change objects in your Active Directory tree.

Next, the Exchange 2000 screen appears. On this screen, you’ll indicate whether you plan to run Exchange 2000 on your network. Sizer needs to know this because Exchange 2000 makes major changes to Active Directory and makes it considerably more complex. If you’re not going to use Exchange, leave the default value of No and click Next.

If you click Yes, you’ll see four new questions appear. Sizer will ask how many messages per day you expect each of your users to send and the average number of recipients those messages will have. You’ll also have to enter the number of Exchange 2000 servers you expect to deploy as well as the number of routing groups.

You’ll then see the first of two Services Using Active Directory screens. The first screen asks if you plan on using Active Directory Integrated Zones in conjunction with Windows 2000’s DNS. If you don’t, leave the default value of No and click Next.

If you click Yes, like the Exchange 2000 screen, you’ll see three questions appear. You’ll need to tell Sizer the number of Dial-In Connections, the DHCP Lease Expiration interval, and the NoRefreshInterval setting for DNS’s Aging And Scavenging feature.

The second Services Using Active Directory screen allows you to enter in the AD activity that will be generated by additional Windows 2000 services. This screen will require some estimating on your part. You’ll need to know what applications you plan to run on your network and whether they’ll affect Active Directory. Few applications take advantage of Active Directory yet, so you’ll probably be okay just leaving these selections blank. However, if you’re unsure about a specific application, check the application’s documentation or call technical support for the application.

When you click Next, you’ll see the Conclusion screen. If you’re unsure about any of your answers, you can click Back to move backwards through the wizard and change an answer. Click Finish to have Sizer calculate the results.

Interpreting the results
When you finish answering the questions in the Active Directory Sizer Wizard, you’ll see the screen shown in Figure C. This screen shows the total number of objects and servers you’ll need for your domain in the right pane. As you can see, Sizer displays the total number of objects you’ll have in your tree along with the number of servers Active Directory will require at a minimum. Sizer will also display the amount of disk space the Active Directory will require.

Figure C
After you complete the wizard, you can view the results.

In the left pane, you’ll see the Site Configuration branch expanded to show the sites and servers recommended by the Wizard. If you click a server, you’ll see the screen shown in Figure D.

Figure D
Sizer will recommend the type of hardware that should work best.

In the right pane, Sizer displays the recommended hardware for a particular site. As you can see, Sizer tells you how fast the server should be, what CPU it should run, how much RAM it has, and the amount and size of the server’s hard drives.

Adding domains, sites, and links
You might be concerned that this tool is too simplistic to handle your remote sites. It’s true that Active Directory Sizer only starts off with recommendations for one domain at one site. However, you can easily add additional domains and sites to Active Directory Sizer to get an overall recommendation for your network. To add an additional site, right-click the previously created domain and select Add Site. This will display the New Site dialog box.

This dialog box is very simple. All you have to do is add the name for the second site along with a subnet. Don’t worry about having the subnet for the additional site be the exact subnet for each site you plan; just enter one to distinguish the site from your original domain. Click OK to create the site.

You’ll then see the site appear in the Site Configuration branch of the left pane. You’ll then need to assign the amount of users from your main domain to the site to represent users that exist at the site. To do so, right-click the site and select Distribute Users.

In the Source Site box in the Distribute Users dialog box, you’ll see Default-First Site, which represents your first domain and contains the total number of users in your domain. The right box, titled Destination Site, contains all of the remote sites. Select the first site, enter the number of users to add to the remote site in the Users To Move box, and then select the target site. Click Apply to make the move and OK to close the box. You’ll then notice that Sizer’s hardware recommendations will change to reflect the changes.

You can add domains and links as well as sites. Every time you make your prospective Active Directory more complex, Active Directory Sizer will react by changing its recommendations.

Try it on for size
After running a few sample domains through the wizard, I would suggest that you use recommendations made by the wizard to be minimums only. It seemed to me that the recommendations made by Sizer were a bit on the small side. Remember that the Active Directory Sizer is only concerned with sizing your server to handle Active Directory traffic. If you’re running additional services on your server or also using it for file and print sharing, you’ll need more power than is recommended by Sizer. That said, the Active Directory Sizer helps to take a lot of the guesswork out of picking the proper hardware for your system.