Article ID: 223140 - View products that this article applies to.
This article was previously published under Q223140
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/256986/EN-US/ )Description of the Microsoft Windows Registry
When you copy or move a file, the negotiated Server Message Block (SMB) size is different. The block size depends on a number of factors including:
When you use Windows NT Explorer to copy a file from the remote computer back to the client, data is typically transfered in Raw mode in 60 KB blocks.
When you use an MS-DOS command prompt command to copy a file in either direction, data is generally transfered in Raw mode. Because Raw mode typically uses a 60-64 KB transfer rate, and Core mode typically uses 4 KB, a Raw-mode transfer is faster.
The factors listed below determine which transfer mode is chosen. However, in this example, what's happening is not getting exclusive use of the Virtual Circuit (VC), which is created when setting up the connection between the two computers. When you cut or copy a file in Windows NT Explorer, make a folder, or perform some other file system changes, Windows NT Explorer will show that change quickly by updating the display. The update in the display is triggered by a call called ChangeNotify.
When copying a file to a remote computer, a long distance ChangeNotify call is triggered. This call goes over the network. This call also prevents getting exclusive use of the VC to copy the file. When copying a file from a remote computer back to the client (command issued locally), the ChangeNotify call is still triggered, but it's now a local call. So the call is not sent over the wire, therefore, the copy operation gets exclusive use of the VC.
Because ChangeNotify is not called for to copy or move a file when you use an MS-DOS command prompt command, these transfers typically use Raw mode.
From the specifications for Core versus Raw mode data transfers: The Windows NT redirector has the following requirements for performing raw mode I/O, all of which must be satisfied for raw mode I/O to occur:
When writing data in Core mode, as in file copy to a remote server, size of data blocks transferred is 4KBytes by default. This can be modified using the following registry parameter on the remote server side.
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
To increase the buffer size, edit the SizReqBuf registry value using the following steps:
(https://support.microsoft.com/kb/152081/EN-US/ )Use of Raw Data Transfer Mode Influenced by Application
Article ID: 223140 - Last Review: November 1, 2006 - Revision: 3.1