Topic Last Modified: 2007-01-08

The Microsoft® Exchange Server Analyzer Tool queries the Win32_Directory Microsoft Windows® Management Instrumentation (WMI) class to determine the value of the Compressed key for the folder containing the Exchange information store database files. If the value for Compressed is set to True for this folder, an error is displayed.

On an Exchange 2000 Server or an Exchange Server 2003 computer, the information store databases are written to the following default location:

<drive> :\Program Files\Exchsrvr\mdbdata

On an Exchange Server 2007 computer, the database files are written to the following default location:

<drive> :\Program Files\Microsoft\Exchange Server\Mailbox\<Storage Group Name>

Microsoft does not support the storage of Exchange data files on an NTFS compressed volume. When you store your Exchange data files on a compressed volume, the additional overhead significantly impacts the performance of Exchange. In addition, after an information store database reaches a certain size (approximately 4 GB), it may fail to mount or it may become corrupt.

The Exchange data files include all the following files:

Files that are managed by the Extensible Storage Engine (ESE) are not designed to be stored on a compressed drive. The ESE depends on sector independence for log-based recovery, and compression of files invalidates sector independence. Compression should not be turned on for volumes hosting ESE databases, or any database that uses write-ahead logging.

Before Exchange 2000 Server Service Pack 3, compressed information store databases were allowed to mount. However, corruption can result in any Exchange 2000 Server information store databases or information store logs that have been compressed by using NTFS compression.

With Exchange 2000 Server Service Pack 3, compressed information store database files of 128 MB or fewer are automatically decompressed. When database files grow to larger than 128 MB, the database does not mount and the error messages are generated in the application log. Exchange 2000 Server Service Pack 3 prevents compressed databases larger than 128 MB from mounting.

To turn off file compression on a given folder

  1. Right-click the folder for which you want to turn off file compression, and then click Properties.

  2. On the General tab, click Advanced.

  3. In the Advanced Attributes dialog box, clear the Compress contents to save disk space check box, and then click OK.

To move the database files on Exchange 2000 Server or Exchange Server 2003

  1. Open Exchange System Manager.

  2. Expand Administrative Groups, expand your administrative group, expand Servers, expand your server, expand your storage group, right-click Mailbox Store, and then click Properties.

  3. On the Database tab, under Exchange database, or Exchange streaming database, click Browse, type the path location to a folder where compression is not enabled, and then click OK.

  4. Click OK or Apply to apply your changes, and then click Yes on the warning message.

    After you click Yes, the stores (databases) are dismounted, moved, and remounted. When these procedures are successfully completed, you receive the following informational message:

    The database files have been moved successfully

To move the location of Exchange storage group database files on Exchange Server 2007

  1. Follow the guidance in the core Exchange Server 2007 documentation, "How to Move a Storage Group Path" (

For more information about .stm and .edb files, see the Microsoft Knowledge Base article 232323, "Native Content Storage in Microsoft Exchange" (