Understanding Public Folder Storage | Microsoft Exchange 2000 Server Adminstrator's Companion

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Public folders are wonderful things, providing centralized storage of virtually any type of document or message and allowing controlled access by any user in the organization. Public folders provide the basis of workflow applications for Exchange 2000 Server.

To manage public folders, you will use the Exchange Folders snap-in as well as the Microsoft Outlook 2000 client. You can create public folders using either of these tools. Much of the creation and management of public folders occurs in the Outlook client because most users work solely in this client, and the administration of public folders was developed to reflect the application with which the users work.

When you create a public folder, that folder is placed in the public folder store of a particular Exchange server. Any Exchange server that has a public folder store can host a public folder. A server might not have a public folder store if, for example, you have made it a mailbox server or dedicated it to some other specific task. A public folder is created in the public folder store of one server but can then be replicated to the public folder stores of multiple additional servers. In a typical organization, the public folders do not all exist on one server; rather, they are distributed across several servers.

An Exchange organization can host multiple public folder trees, with each tree consisting of a separate hierarchy of public folders. Within a public folder tree, the folders at the first level are referred to as top-level public folders. When a user creates a top-level public folder, it is placed in the public folder store on that user's home server. When a user creates a lower-level public folder, it is placed in the public folder store containing the parent folder in which the new folder is created. In addition, each public folder can be replicated to other servers in the organization. As you can see, this situation can get complicated. Public folders exist on different servers, and some public folders have instances on multiple servers.

NOTE
In previous versions of Exchange Server, an organization could have only one root-level public folder (and, therefore, one hierarchy), named All Public Folders. In Exchange 2000 Server, you can create multiple root-level public folders, called public folder trees, that appear alongside (or in place of) the All Public Folders tree. Each public folder tree uses a separate database on an Exchange server. Unfortunately, only the initial tree is visible from within MAPI clients such as Microsoft Outlook. Other trees can be viewed only from OWA, Windows Explorer, or another application through the Installable File System. You will learn how to create new public folder trees later in this chapter.

To ensure that information about public folders is distributed throughout the Exchange system, Active Directory maintains a public folder hierarchy for each public folder tree. This is a single hierarchical structure that contains information about all of the public folders in that tree. The public folder hierarchies are automatically made available to every Exchange user in the organization.

A public folder is considered to have two parts. The first part is the public folder's place in the public folder hierarchy. The second part is the public folder content—the actual messages inside the public folder. The contents of a public folder exist on a single server, unless you specifically configure the content to be replicated to other servers.

REAL WORLD Dedicated Public Folder Servers
Some administrators prefer to use dedicated public folder servers. A dedicated public folder server is one from which the mailbox store has been removed. Dedicated public folder servers are useful in large organizations in which large amounts of public data and frequent access to that data consume a great deal of server resources. To use dedicated public folder servers in your organization, follow the steps listed below. When you finish these steps, you're ready to create your public folders.

Decide which servers you want to have as your dedicated public folder servers.

Remove the mailbox store from the servers you've chosen to be dedicated public folder servers. To do so, simply find the Server container for the appropriate server in the Exchange System snap-in and delete the Mailbox Store configuration object from that server's Information Store container. Be careful when deleting the mailbox store from existing servers; any mailboxes in the store will also be deleted.

Remove the Public Folder Store configuration object from all of your organization's servers that will not host public folders. To do so, delete the Public Folder Store configuration object from the server's Information Store container. If the public folder store you want to remove already holds public folders, you must make sure that current replicas of those folders exist on other servers before deleting the object.