Tools and Checklists

Domain Selection Matrix

This section discusses various tools and checklists useful in selecting your domain model.

It is useful to view the characteristics of the domain models side by side, to match the characteristics and benefits of each implementation model to the needs of your organization. If the needs of your organization change over time, you can review this matrix to determine if the optimal implementation model should change. Conversely, if you have established an implementation model already, you might review this chart to see which additional benefits or trade-off decisions are related to an alternative domain model strategy.

Domain Selection Matrix


Domain Attribute	Single Domain	Single Master Domain	Multiple Master Domain	Independent Single Domains w/Trust relationships

less than 40,000 users/domain	x	x
more than 40,000 users/domain			x
centralized account management	x	x	x1
centralized resource management	x
decentralized account management			x1	x
decentralized resource management		x	x	x
central MIS	x	x	x
no central MIS				x

1 It is possible to have either centralized or decentralized account management under the multiple master domain model.

Location Considerations Checklist

• Where will users log on? Ensure adequate access to an authenticating BDC.
• Do users need to be able to log on from more than one location? If so, their account cannot be tied to that location, implying a single master domain or multiple master domain model.
• What are the availability requirements?
• Does a user need to be able to log on if the WAN to the central location is down (for example, if all data is central and no local processing can be done)?
• How fast are the WAN links? The speed of the links needed between locations should be determined by the usage of resources across the links, and also the frequency of changes to user/group settings.

Hardware Requirements

When selecting a computer for use as a PDC or BDC, use the following hardware guidelines:

PDC/BDC Hardware Requirements


SAM file size	Number of User accounts1	Minimum CPU Needed	Required RAM2

5 MB	up to 3000	486DX/33	32 MB
10 MB	7500	486DX/66	32 MB
15 MB	10,000	Pentium, MIPS, Alpha AXP	48 MB
20 MB	15,000	Pentium, MIPS, Alpha AXP	64 MB
30 MB	20,000 - 30,000	Pentium, MIPS, Alpha AXP	128 MB
40 MB	30,000 - 40,000	Pentium, MIPS, Alpha AXP	166 MB

1 User account numbers are approximate. The exact SAM file size is dependent on the number of user accounts, machine accounts, and group accounts.

2 RAM memory should equal at least 2.5 times the size of the SAM.

For more information, refer to the Large Domain Testing Overview document, available from Microsoft Product Support services.

How Many Domains Are Needed?

As described earlier, the number of users in a domain is a function of the size of the SAM database. The following chart can help you determine the number of domains you need. Note that the single domain and single master domain models can accommodate at least 26,000 user accounts if both user accounts and machine accounts are stored in the SAM database.

How Many BDCs Are Needed?

The ratio of workstations to servers in a domain is a way of maintaining a level of responsiveness during the logon process. Additional backup domain controllers (also called domain servers) allow for more users to log on simultaneously. One BDC can support up to 2000 users.

The server configuration in this table is a 486/66 with 32 MB of RAM, running Windows NT Server.

BDCs per Number of User Accounts

Number of workstations	Number of BDC Servers

10	1
100	1
500	1
1,000	1
2,000	1
5,000	2
10,000	5
20,000	10
30,000	15

Consider performing the initial setup of all BDCs on-site or over high speed links, because each new BDC will need a full synchronization with the PDC. At many companies, BDCs are set up at the same site as the PDC and then shipped to the intended location. This is the most efficient alternative for sites that have only low-speed or RAS access.