Exchange Public Folder Best Practices: Managing Data
After you have planned and deployed a public folder solution in your organization, you must implement a data management plan.
At a high level, managing public folder data means managing database size and growth. Database size affects the following functions:
Backup and restore times
Online maintenance time
Therefore, it is critical to the maintenance of an efficient public folder deployment that you control database size and monitor growth of the public folder databases. This article discusses the following aspects of data management:
Planning for capacity on public folder databases
Content expiration and size limits
This article assumes that you understand basic public folder concepts. For a description of these concepts, see Chapter 7, "Managing Mailbox Stores and Public Folder Stores,” in the Exchange Server 2003 Administration Guide.
There are two elements to consider when you plan for capacity on a specific public folder database. First, you must determine how much data that you will store on a database. After you know how much data that you will store on a database, you can determine the database size. Second, you must monitor and quantify the growth rate on a specific public folder database. By monitoring the growth rate of each database, you can maintain the database at or below the optimal capacity.
The general rule for determining database size is to multiply the amount of data that you will be storing on the database by a scaling factor of 1.6. This scaling factor of 1.6 represents the database overhead that is required to prepare and maintain database indexes and to perform maintenance. For example, if your database must store up to 1 GB of data, you should plan to implement a 1.6-GB database.
The scaling factor of 1.6 is a general guideline that is based on averages. The scaling factor of 1.6 has been determined through testing at Microsoft. It is not a best practice to run public folders on databases that are less than 1.6 times the size of the data.
The monitoring and quantifying of growth are critical parts of capacity planning and data management on a public folder database. At a minimum, you should monitor the growth rate on a server-by-server basis to prevent the overloading of a single server. Ideally, you should monitor overall database and individual folder growth. By understanding growth rates at the database level, you are better prepared to prevent growth database problems.
Also, you should note that replicated data can have a direct effect on growth rates. Periodically examine the daily amounts of content replication and hierarchy replication. To track this growth, note the physical growth on the disks where the data is stored.
Finally, if you are upgrading from Exchange Server 5.5 to Exchange 2000 Server or Exchange Server 2003, you should plan for some growth on the Exchange 2000 Server or Exchange Server 2003 mailbox store. This growth occurs because of public folder replication from Exchange Server 5.5 to Exchange 2000 Server or Exchange Server 2003. This growth occurs even if there are no mailboxes on the Exchange 2000 Server or Exchange Server 2003. For more information, see the Microsoft Knowledge Base article, Mailbox Store Grows When You Replicate Public Folders from Exchange Server to Exchange 2000.
Online database maintenance in Exchange Server is very important. Online database maintenance includes the following tasks:
Dumpster cleanup, which means the deletion of messages that have passed their deleted item retention date
Public folder expiry, which means messages in public folders expire after a certain date has passed
Cleanup of deleted mailboxes
Online defragmentation, which means the detection and removal of database objects that are no longer being used, thereby freeing additional database space
These processes keep the Exchange Server computer healthy and the performance stable. It is a general best practice to run online maintenance at least four hours a day. More specifically, make sure that a full online maintenance schedule is completed at least once a week. Failure to do so harms performance over time.
It is recommended that you configure online database maintenance to run on each database, including mailbox stores and public folder stores for four hours each day. Stagger the online maintenance intervals with the backup schedules. For example, if backup runs from midnight to 2:00 A.M., run online maintenance from 3:00 A.M. to 7:00 A.M.
This staggered schedule is important because online maintenance will not start if the backup session is still running. If an overlap occurs, backup takes precedence over maintenance. In this case, Exchange Server checks every 15 minutes to see if backup has completed. After backup is finished, maintenance will start.
During online maintenance, 18 tasks are performed. Once a task has started, it must finish, regardless of the maintenance timing window. However, maintenance will not start a new task if the maintenance timing window has expired. Therefore, in some instances, not all tasks are finished during a specific maintenance interval. If maintenance is stopped before a task is finished, during the next maintenance cycle, the task will start again where it stopped.
To enable online database maintenance
Open Exchange System Manager.
Expand Servers, and then expand the server that you want to work with.
Expand the storage group that you want to work with.
In the list of available data stores in the details pane, right-click the store that you want to work with, and then click Properties.
In the Store Properties dialog box, click the Database tab.
Perform one of the following procedures:
In the Maintenance interval list, select an interval.
Alternatively, click Customize to gain access to the Schedule dialog box, and then create a custom interval.
For more information about online database maintenance, see "Configuring Store Maintenance and Backup Options" in Chapter 7, "Managing Mailbox Stores and Public Folder Stores," in the Exchange Server 2003 Administration Guide. Also, see JeremyK's Microsoft WebLog, Store Background Processes Part I - IS Maintenance.
Enforcing Content Expiration and Size Limits
Another important task when you manage data on public folder databases is the enforcement of appropriate policies for content expiration and size limit.
Make sure that you implement limits on the folders before you make them available to users. This practice is important for many reasons:
There are practical limits for backing up and restoring databases. These limits will likely be bound by the service level agreement (SLA) that you may have with your users. For example, if your SLA requires that a specific mission-critical folder be available 99.9999 percent of the time, the size of the database that stores that mission-critical content will be bound by the time it takes to restore it. .
Public folders are frequently used as public archives. Therefore, they are likely to fill up unless you impose controls. Note that it is not a best practice to allow users to use public folders as personal, private archives for mail.
You can configure expiration policies on public folders to delete postings that are older than a certain age. However, this procedure is not appropriate for certain types of public folders, such as those folders that store contact details.
You may want to configure limits on typical public folders that are used for simple posts. For example, configure the limits on public folders that are used for simple posts to 20 MB and the limits on archive folders to 100 MB. However, you may not want to configure limits on a Contacts folder to make the space unlimited.
You configure public folder limits on the public folder store just as you configure mailbox limits. However, you can configure individual public folder limits to override the limits that you set on the store.
To perform an in-place restore, it is recommended that your disks have at least as much free space as the size of the database itself plus at least 10 percent. For example, a 35-GB database should run on an 80-GB partition.
Remember that the retention time for deleted items also affects the size of a public folder store because items are not actually deleted until after the retention time for deleted items has expired.
For more information about setting storage and expiration limits on public folders, see the following Microsoft Knowledge Base articles:
For More Information
To learn more about public folders in Exchange Server, see the following resources: