Offloaded Data Transfers fail on a computer that is running Windows 8 or Windows Server 2012

Applies to: Windows 8Windows 8 EnterpriseWindows 8 Pro


Important The hotfix that corresponds to KB 2796995 has been included with the hotfix KB 2848344, which contains all fixes that were previously included in KB 2796995.

Consider the following scenario:
  • You create two Logic Unit Numbers (LUNs) on a third-party storage device.
  • You connect a computer that is running Windows 8 or Windows Server 2012 to the third-party storage device.
  • You assign the LUNs to the computer.
  • You copy a large amount of data by using the third-party storage device.
  • Then you use the Offloaded Data Transfers (ODX) feature to copy files from one LUN to another LUN.
In this scenario, the copy operation freezes at 99 percent.


This issue occurs because the copy engine incorrectly initializes regular copy chunks. Therefore, the copy engine restarts the entire copy process for the file when nonzero bytes are copied through the ODX. When the copy engine restarts, the destination file size is incorrectly set if all the following conditions are true:
  • The copy type is noncached.
  • Nonzero bytes are copied through the ODX.
  • The file size is not aligned to a sector boundary.
Note The expected behavior is that when nonzero bytes are copied through an ODX copy, the copy engine restarts a regular copy from where the ODX copy failed.


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must be running Windows 8 or Windows Server 2012.

Registry information

To apply this hotfix, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

More Information

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates