Procedure 12: Configuring CARP load factor

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You can configure the member servers so that different servers have different loads. The load factor determines how to divide the load among members of an array. Changing this value increases or decreases the load on an ISA Server computer. For example, if one server in the array has a disk four times as large as all the other member servers, you can configure that server to receive a proportionate amount of the cache load, by configuring its load factor relative to that of the other servers. The load factor is a fraction of the total load factors that you configure. For example, if you have two servers, and you want one to handle 4/5 of the requests, you would assign that server a load factor of 4, and the second server a load factor of 1. The server with a load factor of 1 will then handle 1/5 of the requests.

Before you configure the Cache Array Routing Protocol (CARP) load factor, you must first activate the cache and enable CARP on the Internal network (so that requests from the Internal network to the Internet are handled using CARP). By default, there are no cache drives defined when you install ISA Server, so no caching takes place.

Activating the cache

To activate the cache, follow these steps.

  1. On one of the ISA Server computers, such as FW-A1, expand Arrays, expand Main, expand Configuration, and click Cache.

  2. In the details pane, click the Cache Drives tab.

  3. In the details pane, select the server on which you want to define cache drives.

  4. In the task pane, on the Tasks tab, click Define Cache Drives.

  5. Select one of the NTFS drives listed in the list box.

  6. In Maximum cache size, type the amount of space on the selected drive to allocate for caching, and then click Set.

  7. Click OK to close the Cache Drives properties.

    Note

    This change will not be applied until you click Apply, but you can do so after configuring CARP.

Enabling CARP

Before you configure the CARP load factor, you have to enable CARP on the network. This procedure takes place on a computer in the ISA Server array, logged on as an array administrator.

To enable CARP on the network

  1. On one of the ISA Server computers, such as FW-A1, expand Arrays, expand Main, expand Configuration, and click Networks.

  2. In the details pane, select the Internal network. In the task pane, on the Tasks tab, select Edit Selected Network. Alternatively, right-click the Internal network in the details pane, and select Properties.

  3. On the CARP tab, select Enable CARP on this network, and then click OK.

Configuring CARP

To configure the CARP load factor, follow these steps. This procedure takes place on a computer in the ISA Server array, logged on as an array administrator.

The procedure title

  1. On one of the ISA Server computers, such as FW-A1, expand Arrays, expand Main, expand Configuration, and click Servers.

  2. In the details pane, select a server. In the task pane, on the Tasks tab, select Configure Selected Server. Alternatively, right-click a server in the details pane, and select Properties.

  3. On the CARP tab, adjust the Load factor up or down, and then click OK.

  4. In the details pane, click Apply to apply your changes. You will receive a notice that you have to restart the firewall service for this change to be applied. Select Save the changes and restart the services and then click OK.

[Topic Last Modified: 09/26/2007]