Drive M Mapping to IFS Is Not Present by Default in Exchange Server 2003

By default, Installable File System (IFS) in Microsoft Exchange Server 2003 is not mapped to drive M or to any other drive letter. By default, IFS is mapped to drive M in Microsoft Exchange 2000 Server. This article discusses the change in behavior in Exchange Server 2003 and describes a method that you can use if you want to enable the drive M mapping to IFS in Exchange 2003.

When you perform a new installation of Exchange 2003 or when you upgrade to Exchange 2003, IFS is not mapped to the M drive. This change was implemented in Exchange 2003 to prevent unintentional data corruption issues that may occur as a result of manually modifying data on drive M, or as a result of file-level virus scanning or backup and restore operations on drive M.

IFS provides access to the Exchange information store by using Win32 file system APIs. IFS supports the \\.\BackOfficeStorage\ namespace. Exchange 2000 also supports the drive namespace. By default, M:\ is used. IFS was first introduced in Exchange 2000 to provide a method to access the Exchange information store by using the standard file system interface. Note that the \\.\BackOfficeStorage\ namespace remains available even when drive M (or another drive letter mapping) is not present.

In some situations, you may want to enable the drive M mapping to IFS. The following are examples of situations where you might want to do so:

• You use Microsoft FrontPage Extensions and the Microsoft Web Storage System.
• You develop programs that use the drive M mapping to IFS.

Important Microsoft does not support using Win32 file system APIs to access drive M.

Note Do not enable the drive M mapping unless you have a specific reason to do so.

To enable the drive M mapping to IFS in Exchange 2003

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: To enable the drive M mapping in Exchange 2003:

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate and then click the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EXIFS\Parameters
4. On the Edit menu, point to New, and then click String Value.
5. Type DriveLetter, and then press ENTER.
6. On the Edit menu, click Modify.
7. In the Value data box, type M, and then click OK.
   
   Note If you want to map IFS to a drive letter other than M, type the drive letter that you want in the Value data box.
8. Quit Registry Editor.
9. Restart the Exchange Information Store service.
   
   Drive M is not visible until you restart the Exchange Information Store service.

Use drive M only when you want to access data that is not MAPI data. If you want to permit users to access the contents of drive M, do so by using Web Folders. Do not share the contents of drive M.

If you want to disable drive M (after you use the procedure that is described earlier in this article to enable it), you may have to run the script that is documented in the following article in the Microsoft Knowledge Base to successfully remove the IFS drive mapping in Exchange Server 2003: For additional information, click the following article number to view the article in the Microsoft Knowledge Base: