Applies to: Exchange Server 2007 SP3, Exchange Server 2007 SP2, Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2007-08-29

This topic identifies the data that is specific to the Microsoft Exchange Server 2007 Mailbox server role. When you are making a disaster recovery plan, you should understand the backup and restore methods available for this data.

Where a Mailbox Server Stores Data

The Mailbox server role hosts mailbox databases, which contain users' mailboxes. Therefore, the Mailbox server role is designed to store large amounts of end-user data. Although you can recover most of the settings for a Mailbox server from the Active Directory directory service by running Setup /m:RecoverServer, your major concern in a disaster recovery scenario for a Mailbox server is the end-user data. Table 1 outlines where the Exchange 2007 Mailbox server role stores configuration and end-user data.

In Table 1, the file paths all start in the root of the Exchange installation folder. The default Exchange installation folder path is C:\Program Files\Microsoft\Exchange Server\.

Table 1   Locations used by the Mailbox server role for configuration and end-user data

Critical data Location Backup method Restore method

Exchange database files, including both mailbox and public folder databases

File system


Exchange-aware backup application

Exchange-aware backup application

Exchange transaction log files that are specific to each storage group

File system


Exchange-aware backup application

Exchange-aware backup application

Exchange Search information that is specific to each mailbox database in a storage group

File system




Offline address book (OAB)

File system

\ExchangeOAB on the Mailbox server that generates the OAB

\ExchangeOAB on the Client Access server (Not required; however, it can save replication time when a new Client Access server is brought online after a disaster.)

File system backup

File system restore, or rebuild the OAB

Offline address book (OAB)

Public folder

Public folder replication or backup

Public folder replication, backup, or rebuild

Windows registry



System state backup or registry export

System state restore or registry import

Exchange Database and Transaction Log Files

An Exchange 2007 mailbox database contains all the end-user information. The database is stored as the following files:

  • Extensible Storage Engine (.edb file)   The Extensible Storage Engine (ESE), formerly referred to as the Joint Engine Technology (JET) database, is used to store all data submitted by Exchange clients. One .edb file is associated with each database. The .edb file size is limited to 16 terabytes by ESE, but the actual database size should be much smaller to satisfy service level agreements (SLA) for downtime.

  • Transaction log files (.log files)   All changes made to the database are first committed to transaction log files. Any time a user modifies data stored in a mailbox or data is added to the mailbox, that change is written to a transaction log file before it is written to the database. The change is immediately committed to the in-RAM database cache and then copied back to disk when the system's load permits. Transaction log files are created sequentially. This sequence is referred to as the log stream. There can be at most 2,147,483,647 log files (0x7FFFFFFF in hexadecimal, because log file names are in hexadecimal) in a log stream. The transaction log files are 1 megabyte (MB) each. The number of transaction log files created depends on the client load on the server.

Use an Exchange-aware backup application such as Microsoft Windows Server 2003 Backup, or some other third-party tool to back up the Exchange database on a regular basis. After transaction log files are committed, they are protected by backups. Exchange deletes transaction log files from the file system. If regular backups are not performed or backups fail, transaction log files accumulate on the file system.

If transaction log files are not committed and deleted, they can fill all available space on your hard disk. At that point, Exchange dismounts your database and stops accepting data until you make more space available on the hard disk.

For more information about the Exchange public folder database, see Managing Public Folders.

For more information about how to back up and restore your Exchange databases, including the public folders and mailbox databases, see Database Backup and Restore.

Exchange Search

The Microsoft Exchange Search Indexer service (MSExchangeSearch) allows users to perform full-text searches of documents and attachments in messages. Search indexes are not stored in Exchange databases. The search index data for a specific mailbox database is stored in a directory in the same location as the database files.

The directory name follows the convention CatalogData-<guid>-<guid> where the first <guid> is the GUID of the database and the second <guid> represents the Instance GUID, which is used in the clustered scenario to distinguish between the nodes. The following is an example folder name:


The typical path for the .edb files and the CatalogData directory is C:\Program Files\Microsoft\Exchange Server\Mailbox\First Storage Group\.

The search index can become unsynchronized with the database after a recovery if transaction log files are played into the recovered database. The Exchange search engine does not read the played log files into the search index. In this situation, you should rebuild the search index catalog.

To rebuild the search index catalog, you must stop the Microsoft Exchange Search Service, delete the old catalog, and then restart the service. This action forces the server to re-create the search index catalog.

For more information about how to recover your Exchange search index, see How to Rebuild the Full-Text Index Catalog.

Offline Address Book

The offline address book (OAB) is a file that contains an offline replica of the information in a given address book on an Exchange 2007 server. It enables Microsoft Outlook clients to look up address book requests without having to connect to an Exchange server. The OAB is stored in the public folder database and on the Mailbox and Client Access servers.

If you are using OAB distribution in public folders, you should back up and restore public folders as usual. If you are using Web distribution, you need to back up and restore the OAB file on your server.

By default, the OAB file is in the following folder on the server that generates the OAB: C:\Program Files\Microsoft\Exchange Server\ExchangeOAB. This location is the authoritative store for the OAB files. You may also back up the <Exchange_install_location>\OAB directory on your Client Access servers that contain the local cached copy of the OAB files. This action is not required, but doing so makes it unnecessary to replicate all the OAB files from the Mailbox server when the Client Access server is brought back online after disaster recovery.