Data Centers

Configuring public folder limits and replication

Public folders can present you with some new challenges. You should configure replication and set limits so public folders don't consume all of your server's hard drive space. Brien Posey shows you how.

In the Daily Feature “Controlling individual public folders in Exchange 2000,” I showed you how to set folder permissions for your public folders. However, there are more things you must do to make public folders safe and secure. Two such things are setting limits on folders so they don’t consume all of the free drive space on your server and configuring replication to make sure you don’t have a single point of failure.

Setting folder limits
The purpose of setting folder limits is to prevent the folder from outgrowing your server. However, when establishing your folder’s limits, there’s more to consider than just the size of your server’s hard drive. For starters, you’ll also need to consider the other folders that may exist on the server.

For example, suppose that your server has a 10-GB hard disk that you use for storing public folders. If you’ve got two public folders, it may make sense to limit each folder to 5 GB. However, you’ve also got to consider the importance of each folder. For example, if one of the folders is just an Internet message board, and the other folder contains critical data, then you may want to limit the size of the Internet message folder to 500 MB and dedicate the other 9.5 GB to the important folder.

To begin placing limits on the server, navigate through the Exchange System Manager tree to your organization | Administrative Groups | your group | Folders | Public Folders. Right-click one of the public folders and select Properties. Select the Limits tab on the server’s properties sheet, as shown in Figure A. This tab contains several simple fields that you can use to control the folder’s behavior.

Figure A
You can place limits on a public folder to prevent the folder from growing too large.

The first option on this tab is a check box labeled Use Public Store Defaults. By selecting this check box, you can set Exchange so that it will automatically apply a default set of limits to the folder. However, I’ve always preferred to set each folder individually, based on the folder’s needs.

The next three items (Issue Warning At [KB], Prohibit Post At [KB], and Maximum Size At [KB]) contain check boxes that you can use to enable or disable the item, and a text box that you can use to input values. You can use these three options to control how large the folder will get. You can tell Exchange to issue warning messages when the folder begins approaching its maximum size, and to stop allowing posts once the folder reaches a predetermined size. The final option in this section allows you to limit the size of individual posts.

The next two sections on the Limits tab can also be set to use the public information store defaults, but again, I’m usually more comfortable setting the values based on the individual folder. The first of these items controls how many days that deleted items will be retained. If you’re tight on disk space, you can set this number to something low like 0 or 1. However, if data recovery is more important to you, you can set a really long retention time—assuming that you have enough free disk space to allow you to do so.

The final option on the limits tab is the Age Limit For Replicas (Days) option. This option controls how many days that objects can exist within a public folder before they are automatically deleted. For example, if you’re using the public folder for an Internet message board, you may not want posts from six months ago to be in the folder. Therefore, you could use this option to clean out old items automatically.

Folder replication
The final tab that needs some explaining is the Replication tab. Public folders can be replicated to other Exchange servers so that users on the other servers may access the public folder from their home server—rather than placing an additional workload on the server that’s actually hosting the public folder.

To replicate a folder to a different server, click the Add button on the Replication tab. When you do, you’ll see a list of other Exchange servers that are available for replication. Select the desired server from the list and click OK.

Once you’ve chosen the servers to which to replicate the folders, you need to select the replication frequency. By default, Exchange is set to use the folder defaults. However, you can use the Public Folder Replication Interval drop-down list to set the replication schedule to run every two hours or every four hours. You can also click the Customize button and use the resulting dialog box to build a custom replication schedule that can replicate public folder data as frequently as every 15 minutes or as seldom as once a week.

At the bottom of this tab, there’s also a section where you can set the replication message priority. By default, the priority is Normal, but you can set the priority to Urgent or Not Urgent.

Public folders can take quite a bit of time to manage properly. You should make sure that you’ve configured them properly so they can’t consume all of the space on your hard drive. Also, you may want to replicate the folders just in case something should happens to your server’s hard drive.

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