XADM: How to Recover Hard Disk Space from Exchange Server Databases

This article describes how to free hard disk space from Exchange Server databases if there is insufficient free disk space to carry out an offline defragmentation.

The Eseutil utility can perform an offline defragmentation, which releases unused hard drive space from Exchange Server databases to the file system. Eseutil requires free hard disk space equal to at least 110 percent of the database size (to create a temporary database that is used in the defragmentation).

If no local drive has sufficient space for an offline defragmentation, you can use one of the three following options, which are expanded on in the "More Information" section of this article:

• Offline defragmentation with redirected temporary database. Redirect the temporary database to another logical drive, such as a mapped network drive or a temporarily installed hard disk.
• Moving information to another server and recreating empty databases. Move all of the information that either one or both of the information store databases contain to another server. Stop the service, delete the databases, and then restart the service to recreate empty databases.
• Offline defragmentation on another computer. Move the database files to another computer, and then perform the offline defragmentation on that computer.

Eseutil is a part of the Exchange Server 5.5 installation and is located in the Winnt\System32 folder. Eseutil can perform an offline defragmentation, which releases unused hard disk space from Exchange Server databases to the file system. Online defragmentation, which the information store runs during the scheduled online information store maintenance period, does not release disk space to the file system. The amount of space that Eseutil releases is approximately equal to the amount of unused space in the databases. For additional information about how to determine free space in the Exchange Server databases, click the following article number to view the article in the Microsoft Knowledge Base: Offline defragmentation requires free hard disk space of at least 110 percent of the database size. For example, Eseutil requires up to 1.10 gigabytes (GB) of free space to defragment a 1-GB Priv.edb database. Eseutil uses this hard disk space to create a temporary database that the defragmentation process uses. By default, Eseutil creates this database in the current working folder of the command prompt session from which Eseutil runs. For additional information about Eseutil free disk space requirements, click the article number below to view the article in the Microsoft Knowledge Base:

Offline Defragmentation with Redirected Temporary Database

You can use free space on another local or network drive by specifying the path and file name for the temporary database. The specified path must be on a lettered drive, not in a Universal Naming Convention (UNC) path. For example, C:\path_name_1\path_name_2\Tmpdfrg.edb is acceptable, but \\file_server\sharepoint\tmpdfrg.edb is not allowed.

You can add a temporary physical drive to the server specifically for defragmentation. You can also map a network drive by using the net use command.

The following sample command specifies the temporary database path and file name G:\Folder1\TempDfrg.edb: Notice that there is no space between the /t and the drive letter.

Note After you defragment your database offline, it has a new signature that does not match the signature in the old log files. Retention of the old log files causes the database to fail to start and the following event ID 143 error message is logged:

"The database signature does not match the log signature for database."

Because the database was shut down correctly before you defragmented it, all the data was written to the database. You can safely move the log files from the production location to a temporary location. Then you can start the database.

Moving Information to Another Server and Recreating Empty Databases

Warning Before you perform the following procedure, back up all Exchange Server databases and verify the databases' integrity. If you do not back up your databases, you may permanently damage or lose your databases.

You can move all of the information from an information store database to another server and then recreate an empty database in the information store database's place to effectively free disk space. If the information store does not find a database where a database should exist, the information store service recreates an empty database.

To move information to another server and recreate empty databases:

1. Use one of the following procedures, as applicable, to move the database information to another computer:
   • Private information store. To move information from the private information store (Exchsrvr\Mdbdata\Priv.edb), use the Move Mailbox utility from the Exchange Server Administrator program to move all of the user mailboxes to another Exchange Server computer. You must move hidden user mailboxes as well. Do not move system mailboxes, such as mailboxes of the Internet Mail Service or directory service; the system services recreate the system mailboxes in the empty database during startup.
   • Public information store. To move information from the public information store (Exchsrvr\Mdbdata\Pub.edb):
     1. Make sure that there is at least one replica of every public folder on the server. Open the public folder properties, click the Properties tab, and then make sure that at least one other server is listed in the Replicate folders to list.
     2. Verify that public folder replication is complete. Open the public folder properties, click the Folder Replication Status tab, and then make sure that replication is complete.
     3. Delete the original public folders. You can also move public folders to another site. For additional information, click the article number about how to move public folders to another site below to view the article about how to move public folders to another site in the Microsoft Knowledge Base:
        154947  (http://support.microsoft.com/kb/154947/EN-US/ ) XADM: How to Move a Public Folder to Another Site
2. Stop the information store service, delete the database for which you moved information to another server, and then restart the information store service. The information store recreates empty databases.
3. Restore the information that you moved to another server.

After you perform these steps, any free space in the database is returned to the file system's available space.

Offline Defragmentation on Another Computer

You can also move the databases to another computer that Microsoft Exchange Server is not installed on and run Eseutil on that computer. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

Quick Reference

The following outline provides a quick reference of the options that are available to free hard disk space from Exchange Server databases.

• Offline defragmentation with temporary database redirected
• Current drive
• Another drive temporarily added to system
• Over network
• Move the database to another computer


• Move all information to another server and delete to start over with empty database
• Private information store. Move mailbox
• Public information store. Remove all instances, and so on


• Move database to another computer and perform offline defragmentation on that computer
• Q244525 - XADM: How to Run Eseutil on a Computer Without Exchange Server
• Public information store. Remove all instances, and so on