MPIO paths do not recover when you use MSDSM in Windows Server 2012

Applies to: Windows Server 2012 DatacenterWindows Server 2012 DatacenterWindows Server 2012 Essentials More


Consider the following scenario:
  • You connect a logical disk through an Asymmetric Logical Unit Assignment (ALUA)-based storage area network (SAN) to a computer that is running Windows Server 2012.
  • You configure the disk as a multipath disk by using Microsoft Multipath I/O (MPIO) and Microsoft Device Specific Module (MSDSM).
  • You perform a path loss test (for example, you suddenly remove the cable or disconnect the controller).
In this scenario, some MPIO paths do not recover as expected. Therefore, you have to restart the server to restore the paths. Over time, this issue could lead to performance problems and possibly to a loss of all paths to one or more logical units.


This issue occurs because the Host Bus Adapter (HBA) miniport driver or storage controller firmware for the device has an internal time-out value for Report Target Port Groups (RTPG) commands that is less than the default time-out value that MSDSM uses for RTPG commands. When an RTPG command is not completed in time, the miniport reports a time-out failure to MSDSM, and the path is not restored correctly. This issue is known to occur with Fibre Channel HBAs from multiple vendors and with SANs that support ALUA.

Note This hotfix increases the default time-out value that MSDSM uses for RTPG commands from 4 seconds to 10 seconds.


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

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, contact 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 Server 2012.

Registry information

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

Restart requirement

You have to 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.

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

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