For a planned Active Directory, how can I predict how much memory will my new Domain Controllers require, and how many of them I need?
The Active Directory service Sizer tool lets you estimate the hardware required for deploying Active Directory in an organization based on the organization’s profile, domain information and site topology.
Based on user inputs and internal formulas, this tool estimates the number of:
Domain controllers per domain per site.
Global Catalog servers per domain per site.
CPUs per machine and type of CPU.
Disks needed for Active Directory data storage.
In addition, the Sizer tool provides approximate estimates for the following:
Amount of memory required.
Network bandwidth utilization.
Domain database size.
Global Catalog database size.
Inter-site replication bandwidth required.
The list of information to be gathered per domain to accurately size the domain controllers includes:
Total number of users in the domain. Total number of concurrent users.
Total number of attributes per user. Active Directory automatically assigns each user a number of attributes. Additional attributes based on the business uses of the Active Directory service should be included in the estimate.
Average number of groups a user belongs to. The number of groups a user belongs to can affect the time to process a logon request. The logon request evaluates user access by looking at the access granted to each group the user belongs to.
Average logon rate per second during peak hours (interactive, batch and network). Interactive logon type is intended for users who will be interactively using the machine, such as a user being logged on using Terminal Services, a remote shell, or similar process. Batch logon type is intended for batch servers, where processes may be executing on behalf of a user without their direct intervention; or for higher performance servers that process many clear-text authentication attempts at a time, such as mail or Web servers. Network logon type is intended for high performance servers to authenticate clear text passwords. This type is used to access other network resources, such as remote servers or printers.
Password expiration rate (in days).
Number of Windows 2000-based computers in the domain.
Number of other computers in this domain.
Number of other objects published in this domain. Other objects are any objects other than users and computers that will be included in Active Directory. For example, user groups, organizational units, contacts, printers or shares would be consider "other objects".
Desired average CPU utilization limit for each Domain Controller.
Preferred CPU type for domain controllers,
Number of processors required of the CPU type specified above.
Administration. This section allows an administrator to specify the administrator-generated workload for object addition, deletion, or modification to Active Directory. The planned average number of objects added, deleted, or modified on a daily, weekly, or yearly interval should be entered.
Microsoft Exchange 2000. Microsoft Exchange 2000 Server uses Active Directory for directory services, transport and name resolution. If planning to install Exchange 2000, enter the average number of messages per user/per day and the average number of recipients for each message.
DNS related issues. This section allows an administrator to specify whether Active Directory-integrated DNS zones will be used, the number of dial-in connections (per day) that will be made by computers joined to the domain, the duration of DHCP leases, and the behavior of the DNS Server aging and scavenging feature.
Other Active Directory-enabled application issues. This section covers other Active Directory-enabled applications that are not specifically known by the tool. Changes introduced by Active Directory Connector (ADC) or other directory synchronization programs (such as Microsoft Directory Synchronization Services) should be estimated in operations per second for searching, adding, deleting, and modifying objects.
Note: These estimates were planned on old Dell POWEREDGE 6300 servers. With today’s hardware available you’d expect Microsoft to produce more up-to-date templates for this useful tool – but they haven’t.