Storage Features of Exchange Server 2003


Microsoft® Exchange Server 2003 includes many improvements the Exchange store. In general, these improvements focus on making disaster recovery operations easier and faster and on streamlining internal processes such as public folder replication.

Specifically, the improvements include the following:

  • Support for the new Volume Shadow Copy service, which is available as part of the Microsoft Windows Server™ 2003 backup API.

  • A new type of storage group (the Recovery Storage Group) provides a temporary location for restored mailbox data. After restoring the mailbox data to the Recovery Storage Group, you can then merge the data you need with the original mailbox store, whether that means restoring the entire mailbox store or a few individual mailboxes.

  • The Microsoft Mailbox Merge Wizard (Exmerge) is now available for download at the Exchange Downloads website (

  • Public folder replication processes are overhauled and streamlined for more efficient use of bandwidth.

  • The Exchange Virus Scanning Application Programming Interface (VSAPI) is enhanced and expanded.

  • New in SP2: You can now configure settings related to the database size limits of Exchange Server databases. For example, you can configure the maximum database size, the threshold at which a warning event is logged, and the time of day at which database sizes are evaluated.

Shadow Copy Backup

Exchange Server 2003 supports the new backup infrastructure implemented in Windows Server 2003. Backup programs (including Microsoft Windows Backup) can use either the existing Microsoft Windows® 2000 backup and restore APIs, or the new APIs. The new APIs use the Windows Volume Shadow Copy service to create a shadow copy (also known as a snapshot) of the disk at the beginning of the backup process. Exchange then uses the shadow copy (rather than the working disk) to create the actual backup, therefore normal operation can continue. This method offers the following advantages over previous methods:

  • A backup of a volume is produced. This backup reflects the state of that volume at the instant the backup started, even if the data changes while the backup is in progress. All the backup data is internally consistent and reflects the state of the volume at a single point in time.

  • Applications and services are notified that a backup is about to occur. The services and applications can then prepare for the backup by cleaning up on-disk structures and by flushing caches and log files.

Using Shadow Copy Backup

The Exchange API provides support for shadow copy backups.

You can still use the Windows  Server 2003 Backup utility to back up Exchange Server 2003 databases (mailbox stores and public folder stores); however, this method uses the existing API's for non-shadow copy backups. Windows  Server 2003 Backup supports backing up your Windows file system using the Volume Shadow Copy service, but it does not support the Exchange Volume Shadow Copy service APIs. To use the new shadow copy APIs to back up databases, you must use a third-party solution.

Recovery Storage Group

To provide greater flexibility when restoring mailboxes and mailbox stores, Exchange 2003 provides a Recovery Storage Group feature. The Recovery Storage Group is a specialized storage group that can exist alongside the regular storage groups in Exchange (even if the server already has four regular storage groups). You can restore mailbox stores from any regular storage group that meets the following conditions:

  • The server housing the storage group is running Exchange 2000 SP3 or later.

  • The server housing the storage group is in the same Administrative group as the server housing the Recovery Storage Group.

  • If you are restoring multiple mailbox stores simultaneously, they must all be from a single storage group.

After you restore a mailbox store to the Recovery Storage Group, move the recovered mailbox data from the Recovery Storage Group to the regular storage group. With this method, you can recover an entire mailbox store (all of the database information, including the log data) or just a single mailbox. Mailboxes in the Recovery Storage Group are disconnected and are not accessible to users with mail clients.


You can only use the Recovery Storage Group to recover mailbox stores, not public folder stores.

Using a Recovery Storage Group

The following procedures represent a simple restore scenario; these procedures assume that you have already backed up your storage groups.

Before you begin these procedures, ensure that you are logged in with an account such as Backup Operators that has Receive As and Send As permissions on all of the Exchange mailboxes. If these permissions are denied, the restore process does not complete.

If you restore mailbox stores without creating a Recovery Storage Group, the data is restored directly to the original mailbox stores, as in previous versions of Exchange.

The process of using a Recovery Storage Group to restore mailbox data consists of three main steps:

  1. Set up the Recovery Storage Group.

  2. Restore a mailbox store to the Recovery Storage Group.

  3. Merge the recovered mailbox data with regular user mailboxes.

For detailed instructions, see "How to Set Up a Recovery Storage Group" in Using Exchange Server 2003 Recovery Storage Groups.


When merging data, folder permissions and inbox rules are not included. Filtering what gets merged is also not supported. If you need this functionality, you can use Microsoft Exchange Mailbox Merge Wizard (Exmerge) instead of the recover data task. The Exmerge utility is available for download at the Exchange Downloads website ( After you restore the appropriate mailbox store to the Recovery Storage Group, start Exmerge and follow the instructions in the wizard to move the mailbox data.

For detailed information about overriding the Recovery Storage Group, see How to Set the Recovery Storage Group Override Registry Key.

Microsoft Exchange Mailbox Merge Wizard

Previously, the Microsoft Exchange Mailbox Merge Wizard (Exmerge) was available as an Exchange Resource Kit tool. Now, the wizard is available for download at the Exchange Downloads Web site. With this wizard, you can move data between identical mailboxes that exist in different mailbox stores; for example, to restore a mailbox from a backup, restore the mailbox store to the Recovery Storage Group, and then use the wizard to merge the restored mailbox data with the original mailbox. For detailed information about how to perform this procedure, see "Using a Recovery Storage Group" earlier in this topic.

Improved Public Folder Store Replication

In Exchange 2003, the public folder replication algorithms have been refined for greater efficiency when backfilling. ("Backfilling" is when a server determines that it has not received all of the updates for a replicated folder and must retrieve the missing updates from another server.) To select a server (or servers) to use as a backfill source, Exchange first creates a list of all of the servers that have some portion of the necessary content, and then sorts the list as follows:

  1. Sorts the list according to the lowest transport cost (servers in the same site have priority over servers in remote sites).

  2. For servers with the same transport cost, sorts again according to newest Exchange version. In previous versions of Exchange, servers running newer Exchange versions are selected over servers running older versions, regardless of the transport cost. For example, a server in a remote site running Exchange 2000 would be selected over a local server running Microsoft Exchange Server version 5.5. In Exchange 2003, transport cost now has greater importance in the selection criteria.

  3. For servers with the same transport cost and Exchange version, sort again according to the largest number of necessary changes available on the server. In previous versions of Exchange, a server holding all of the necessary updates is chosen over a server holding only some of the updates, regardless of transport cost. In Exchange 2003, this preference has been changed so that if some updates are available on a server with a lower transport cost, that server is selected to backfill those updates, even if the rest of the updates must be obtained from other (higher-cost) servers.

As an example of how the new behavior differs from that of all Exchange 2000 Server versions, consider an Exchange 5.5 deployment of several sites (with multiple servers per site, all replicating public folders) that must be upgraded to Exchange 2003. Add one Exchange 2003 server to each site. In each site, the Exchange 2003 server will backfill its public folders from the local Exchange 5.5 servers, rather than search for a newer server in one of the remote sites.

Improved Virus Scanning API

Exchange 2000 SP1 delivered the Virus Scanning API (VSAPI) version 2.0, which provided improved support for scanning Internet content and reporting on the sender and receiver of the virus. Exchange 2003 improves the VSAPI by allowing antivirus vendor products to run on Exchange servers that do not have resident Exchange mailboxes (for example, gateway servers or bridgehead servers). The Exchange 2003 VSAPI version 2.5 allows antivirus vendor products to delete an infected message and send a notification message to the sender of the infected message. The vendor products can also create additional virus status messages to allow clients to indicate the infection status of a particular message. For more information about antivirus applications that use the new VSAPI features, contact your antivirus manufacturer.

New in SP2: Database Size Limit Configuration and Management

With Exchange Server 2003 Service Pack 2 (SP2), you can now customize settings related to database size limits to meet the needs of your organization. SP2 adds the following primary features.

  • You can configure a logical database size limit for each of your Exchange databases. The logical size of the database equals the physical size of the .edb file and the .stm file minus the logical free space in each. The limitation of this feature depends on the version of Exchange Server 2003 you are running:

    • Exchange Server 2003 Standard Edition   By default, the size limit of each database on a server running Exchange Server 2003 Standard Edition is 16 GB. After you install Exchange Server 2003 SP2, the default size limit for each Exchange database is 18 GB. Additionally, you can configure database size limits of up to 75 GB for each database on servers running Exchange Server 2003 SP2.

    • Exchange Server 2003 Enterprise Edition   By default, the size limit of each database on a server running Exchange Server 2003 Enterprise Edition is 8,000 GB. This size is generally a theoretical limit. The actual limit of an Exchange database is based on your server hardware and on the hardware of your storage subsystem. After you install Exchange Server 2003 SP2, you can customize the database size limit to a value up to 8,000 GB.

  • A warning event is logged in the Application log when a server running Exchange Server approaches the database limit that you configured for a specific database. You can specify the threshold at which you want to be notified. By default, the threshold for logging a warning event is when 90 percent of the maximum logical database size is consumed.

  • An error event is logged in the Application log when a server running Exchange Server reaches the database limit that you configured for a specific database. Additionally, Exchange immediately takes the database that exceeded the database limit offline. To temporarily restore e-mail service for your users on the database that reached the configured limit, you can restart the database. However, the database will be dismounted on each daily check that determines that the logical size limit for the database has been exceeded.

  • You can specify the time each day that Exchange Server checks database size limits based on the limits you have configured. By default, Exchange Server checks the size of each Exchange database at 5 hours after midnight (05:00).

For information about how to configure storage limits, see the following:

Disaster Recovery Planning Considerations

If you change the size limit of your Exchange databases, you may want to re-evaluate your Exchange database backup and restore plan. Specifically, if you increase the size limit of the Exchange databases, be sure to test your backup and recovery operations using the new database size limits to make sure that you can still meet your service level agreements. For example, if the previous size of a mailbox store was 15 GB and you were able to meet your service level agreement by recovering the data in less than 8 hours, you may no longer be able to recover the database that quickly if you increase the size of a mailbox store to 20 GB or larger.

For information about service level agreements, see "Establishing a Service Level Agreement" in "Setting Availability Goals" in the Exchange 2003 High Availability Guide.

For information about how to configure storage limits, see the following: