Performing Capacity Planning
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
The flowchart in Figure 5.9 outlines the capacity planning process for ISA Server.
Figure 5.9 ISA Server Capacity Planning Process
.gif "ISA Server Capacity Planning Process")
Use the following guidelines for capacity planning:
Ensure the minimum hardware requirements deploying ISA Server are met.
Decide whether to install ISA Server as a firewall. If yes, ensure that the minimum firewall requirements are met.
Decide whether or not to install ISA Server as a Web cache server. If yes, ensure that the minimum hardware requirements are met.
The following list describes the minimum hardware requirements for installing ISA Server:
A computer with a 300 megahertz (MHz) or higher Pentium II-compatible CPU.
The computer must be running either a member of the Windows 2000 Server family, or a member of the Windows Server 2003 family. If you are installing ISA Server on a computer running Windows Server 2003, you must also install ISA Server SP1.
Note
- Using the latest service pack is always recommended.
256 megabytes (MB) of memory.
20 MB of available hard disk space.
A network adapter to communicate with the internal network.
One local hard disk partition that is formatted with the NTFS file system.
To implement the array and enterprise-level policy configuration, you must also run Active Directory.
If you are using ISA Server in firewall or integrated mode, two network adapters are required.
If your ISA Server is also supporting other services, such as e-mail or Web services, additional resources might be required.
Use Table 5.3 to determine the type of computers to use and whether you require an array.
Table 5.3 Hardware Requirements for Different Network Loads
| Hits per Second | Minimum Hardware Required | RAM |
|---|---|---|
Less than 500 |
One computer, Pentium II, 300 MHz processor |
256 MB |
500 to 900 |
One computer, Pentium III, 550 MHz processor |
256 MB |
More than 900 |
One computer, Pentium III, 550 MHz processor, for each 800 hits per second increment |
256 MB per server |
Note
- You can also use Performance Monitor to identify bottlenecks and determine whether to add more servers.
If multiple computers are required to handle the network load, consider setting up an array of ISA Server–based computers. Arrays allow Web cache routing across a group of ISA Server–based computers. For more information, see "Configuring ISA Server in an Array" later in this chapter.
Firewall Requirements
Table 5.4 lists hardware requirements and network connections based on expected throughput for firewall clients accessing content on the Internet.
Table 5.4 Hardware Requirements for Firewall
| Throughput Requirements | Minimum Hardware Required | Internet Connection Type |
|---|---|---|
36 Kilobits per second (Kbps) to 1 Megabits per second (Mbps) |
One computer, Pentium II, 300 MHz processor |
POTS modem, cable modem, or xDSL |
384 Kbps to 1.5 Megabits per second (Mbps) |
One computer, Pentium II, 300 MHz processor |
T1 |
3 Mbps - 44 Mbps |
One computer, Pentium III, 550 MHz processor |
T3 or faster |
More than 44 Mbps |
One computer, Pentium III, 550 MHz, for each 50 MB/second required |
OC3 or faster |
Forward Caching Requirements
You can deploy ISA Server as a forward-caching server, which maintains a centralized cache of frequently-requested Internet content. In this case, consider how many users might access the Internet.
Table 5.5 lists the hardware requirements for using ISA Server in forward cache mode.
Table 5.5 Hardware Requirements for Forward Caching
| Internet Users | Minimum Hardware Required | RAM | Disk Space for Caching |
|---|---|---|---|
Up to 500 |
One computer, Pentium II, 300 MHz processor |
256 MB |
2–4 Gigabytes (GB) |
500 -1,000 |
One computer, two Pentium III, 550 MHz processors |
256 MB |
10 GB |
More than 1,000 |
Two computers, Pentium III, 550 MHz processors |
256 MB for each server |
10 GB for each server |
If your user-base exceeds 1,000 users, you can use hardware with faster processors and more memory, or you can add more ISA Server installations.
Reverse Caching Requirements
You can deploy ISA Server as a reverse-caching server to fulfill Web requests from the Internet to your network. For example, you might place an ISA Server computer between the Internet and an organization’s Web server that is hosting a commercial Web business or providing access to business partners. In that case, you need to consider how often external clients might request content from the publishing servers.
Table 5.6 lists hardware requirements for ISA Server in reverse cache mode, based on the number of hits per second from Internet users.
Table 5.6 Hardware Requirements for Reverse Caching
| Hits Per Second | Minimum Hardware Required |
|---|---|
Fewer than 100 |
One computer, Pentium II, 300 MHz processor |
101 to 250 |
One computer, Pentium III, 450 MHz processor |
More than 250 |
One computer, Pentium III, 550 MHz processor for each 250 hits per second. You can use Performance Monitor to determine bottlenecks, and then add more servers or more powerful hardware, as necessary. |
Memory requirements depend on the size of the cacheable content that you are publishing, and the working set of the content. Ideally, all cacheable content should fit into the available memory. By default, the ISA Web Proxy service uses half of the available server memory for RAM caching. For example, if the Web site you are publishing has 250 MB of cacheable content, then your ISA server computer should have at least twice this much available RAM before the Web Proxy service starts.
Adding Computers
In some cases, you need to decide whether to add an additional ISA Server–based computer or to improve the performance of the existing computer by adding an additional processor. Each option has different advantages.
When you add a new computer and create an array of ISA Server–based computers, you set up a fault-tolerant system. If one computer fails, the other continues to function. On the other hand, adding a computer means that you have to purchase and manage additional hardware and any software that is installed on the computer.