Locating Folders by Using Affinities

When you select a public folder to view its contents, the information store must decide where that folder is located. The information store looks for the public folder in the following places in this order:

1. The user's public folder hierarchy server.
2. A random number server in the site. If there are multiple replicas in the site, the store provider uses an algorithm that is based on the user's domain name to determine the next location to search. The resulting number is divided by the number of servers that contain the public folder in the site. A connection is then made to the server assigned to that number. Because the number is random, this method distributes connections across all available replicas in the site.
3. An existing connection server in the site. If the information store cannot connect to the random number server, the remaining servers in the site are tried. Servers that already have established remote procedure call (RPC) connections are tried first.
4. Other sites. If no public folder replicas are available in the site but there are replicas in at least one other site, the affinity number is used to determine the order in which connections are attempted.

   The affinity number is set in the site's Public Folder Affinity property page. This setting allows an administrator to set a cost for each of the other sites in the organization. The cost determines the order in which the information store attempts to connect to sites. The site with the lowest cost is the one to which the information store first tries to connect.

   After the information store finds the site, the servers within that site or group of sites are tried in random order. If two sites have the same cost, the servers in those sites are pooled together and tried in random order. The information store does not attempt to connect to a site with no affinity setting.

In the following illustration, a user in Site 1 wants to connect to a public folder. All of the servers shown have a replica of the desired public folder. The numbers in the servers indicate the order in which the connections are attempted.