Slow performance when you use a mapped drive to copy files to a remote server from a Windows Server 2003-based computer

You may notice slower than expected copy performance if you use the Server Message Block (SMB) protocol to copy files from a computer that is running Microsoft Windows Server 2003 or from a Windows Server 2003 Terminal Services session to a computer on your network that is running Microsoft Windows 2000 Server or Microsoft Windows NT 4.0 Server. You experience these symptoms if you use a mapped drive to connect to the network share. When you analyze a network capture, Network Monitor shows the following excessive SMB Notify Change traffic: You do not experience these symptoms if you connect to the network share by using a UNC path.

This issue may occur if a delayed TCP/IP acknowledgment, also known as a TCP ACK, occurs in an "SMB: C NT transact - Notify Change" packet. Typically, this issue occurs if you use Windows Explorer to copy a large number of files and folders. Change Notify requests in Windows Explorer occur more frequently when you use a mapped drive than when you use a UNC path to connect to the network share. Therefore, users who are logged on to a Windows Server 2003 Terminal Services session and who use a mapped drive may experience performance issues with Windows Explorer.

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 work around this issue, follow these steps:

1. Install the hotfix that is documented in the following article in the Microsoft Knowledge Base:
   831129  (http://support.microsoft.com/kb/831129/ ) Folder tree flickers when you view a mapped network drive in Microsoft Windows Explorer
2. Add the NoRemoteRecursiveEvents registry entry to the following registry subkey, and then set the entry to 1:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
   When you set the NoRemoteRecursiveEvents registry entry to 1, Change Notify requests are turned off for file and folder changes that occur in subfolders of a mapped network share. The server still sends a Change Notify event when a file or a folder is changed in the root and first folder level of the mapped network share. However, the server does not send a Change Notify event when a change is made at the level of the second subfolder or deeper in the mapped network share.
   
   To add the NoRemoteRecursiveEvents registry entry to the following registry subkey, and then set the entry to 1, follow these steps:
   1. Click Start, click Run, type regedit, and then click OK.
   2. Locate and then click the following registry subkey:
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
   3. On the Edit menu, point to New, and then click DWORD Value.
   4. Type NoRemoteRecursiveEvents, and then press ENTER.
   5. On the Edit menu, click Modify.
   6. Type 1 in the Value data box, and then click OK.
   7. Quit Registry Editor.

To determine whether you are experiencing this issue, map a drive to a network share, and then copy a folder to the network share. Use a UNC path to connect to the network share, and then copy the same folder to the network share. Compare the Network Monitor captures of both copy operations, and then see whether the captures show excessive SMB Notify Change traffic.

For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base: