Microsoft KB Archive/941673

= After you add the CopyFileBufferedSynchronousIo registry entry in Windows Vista, a file copies only slightly more quickly when you use Windows Explorer to copy the file to another computer =

Article ID: 941673

Article Last Modified on 9/11/2007

-

APPLIES TO


 * Windows Vista Home Premium
 * Windows Vista Ultimate
 * Windows Vista Business
 * Windows Vista Home Premium 64-bit Edition
 * Windows Vista Ultimate 64-bit Edition
 * Windows Vista Business 64-bit Edition
 * Windows Vista Enterprise 64-bit Edition

-



Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SYMPTOMS
In Windows Vista, you add the CopyFileBufferedSynchronousIo registry entry to improve the speed of a file copy operation. However, when you use Windows Explorer to copy a file from the Windows Vista-based computer to a computer that is running an older Windows operating system, the file copies only slightly more quickly.

Note The file copies more quickly if you use a command-line tool to copy the file. You can use command-line tools such as Robocopy.exe and Xcopy.exe to copy the file.



CAUSE
This problem occurs because Windows Explorer does not check for the CopyFileBufferedSynchronousIo registry entry.

In Windows Vista, the CopyFile function creates a non-cached I/O request to perform a write operation. Therefore, the speed of the file copy operation is affected by the disk speed and by other resources on the older operating system.

The CopyFileBufferedSynchronousIo registry entry reverts the CopyFile function in Windows Vista to its earlier behavior. After you add the registry entry, you expect the CopyFile function to work as it would in an earlier Windows operating system. However, because Windows Explorer does not check for this registry entry, this problem occurs.



RESOLUTION
To resolve this problem, apply the following hotfix. After you apply this hotfix, Windows Explorer checks for the CopyFileBufferedSynchronousIo registry entry.

Note This hotfix takes effect only if you add the CopyFileBufferedSynchronousIo registry entry and set its value to 1.

Hotfix information
A supported hotfix is now available from Microsoft. However, it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites
No prerequisites are required.

Restart requirement
You have to restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

Registry information
To use one of the hotfixes in this package, you do not have to make any changes to the registry.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Vista, 64-bit versions


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To add the CopyFileBufferedSynchronousIo registry entry, follow these steps:  Click Start, type regedit in the Start Search box, and then press ENTER. Locate and then click the following registry subkey:

 On the Edit menu, point to New, and then click DWORD Value. Type CopyFileBufferedSynchronousIo to name the new entry, and then press ENTER. Right-click CopyFileBufferedSynchronousIo, and then click Modify.</li> In the Value data box, type 1, and then click OK.</li> Exit Registry Editor.</li></ol>

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684Description of the standard terminology that is used to describe Microsoft software updates

Additional query words: shell

Keywords: kbfix kbqfe kbpubtypekc kbexpertiseadvanced kbexpertisebeginner kbhotfixserver KB941673

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.