Symptoms

Consider the following scenario:

  • You connect a computer that is running Windows Server 2008 or Windows Server 2008 R2 to a storage device.

  • You configure Microsoft Multipath I/O (MPIO) and Microsoft Device Specific Module (MSDSM) to control the storage device.

  • You perform a surprise removal of one path to the storage device. This behavior starts the failover operation to the remaining path.

In this scenario, the MSDSM reports that it did not return a valid path even though there is at least one valid path. Therefore, I/O requests to the logical unit number (LUN) are not switched to the other path, and the storage connectivity is not fully functional.

Additionally, the following System event log entries are reported:



Without a valid path, I/O to the MPIO disk fails, and the MPIO disk is torn down. A dialog box that indicates that delayed writes failed is displayed, and the following System event log entry is reported:

Cause

This issue occurs because the Microsoft Multipath I/O (MPIO) driver (mpio.sys) incorrectly starts two failover requests for the same failed path.

A race condition in the MPIO failover handling leads to multiple attempts at removing the same failed path. When I/O fails on one device and starts the failover on that device, another device that is in the same failover group (for example, has the same Path ID) also fails over. If there is no failed I/O on the second device for the failover, the state of the second device goes straight from NORMAL to DEGRADED. The reason why the state goes from NORMAL to DEGRADED is that the device does not complete FAILOVER/WAIT1/WAIT2 states, and the state does not wait for the I/O to be completed on the device. The issue occurs when an I/O is completed after the failover is finished.

Resolution

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 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:

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

Prerequisites

To apply this hotfix, you must be running one of the following operating systems:

  • Windows Server 2008

  • Windows Server 2008 Service Pack 2 (SP2)

  • Windows Server 2008 R2

  • Windows Server 2008 R2 Service Pack 1 (SP1)

For more information about how to obtain a Windows Server 2008 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

968849 How to obtain the latest service pack for Windows Server 2008

For more information about how to obtain a Windows 7 or a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To use the hotfix, you do not have to change 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.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows Server 2008 file information notes

Important Windows Vista hotfixes and Windows Server 2008 hotfixes are included in the same packages. However, only "Windows Vista" is listed on the Hotfix Request page. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows Vista" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

    Version

    Product

    SR_Level

    Service branch

    6.0.600
    1.
    22xxx

    Windows Server 2008

    SP1

    LDR

    6.0.600
    2.
    22xxx

    Windows Server 2008

    SP2

    LDR

  • Service Pack 1 is integrated into the release version of Windows Server 2008.

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008" section. MUM files and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Mpio.sys

6.0.6001.22876

105,872

12-Mar-2011

16:27

x86

Mpio.sys

6.0.6002.22610

106,384

12-Mar-2011

16:27

x86

For all supported x64-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Mpio.sys

6.0.6001.22876

129,936

12-Mar-2011

16:22

x64

Mpio.sys

6.0.6002.22610

130,448

12-Mar-2011

16:22

x64

For all supported IA-64-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Mpio.sys

6.0.6001.22876

289,168

12-Mar-2011

16:19

IA-64

Mpio.sys

6.0.6002.22610

290,192

12-Mar-2011

16:19

IA-64

Windows Server 2008 R2 file information notes

Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:

    Version

    Product

    Milestone

    Service branch

    6.1.760
    0.20xxx

    Windows Server 2008 R2

    RTM

    LDR

    6.1.760
    1.21xxx

    Windows Server 2008 R2

    SP1

    LDR

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 R2" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x64-based versions of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Mpio.sys

6.1.7600.20959

156,544

04-May-2011

05:18

x64

Mpio.sys

6.1.7601.21720

156,544

04-May-2011

05:29

x64

For all supported IA-64-based versions of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Mpio.sys

6.1.7600.20959

353,664

04-May-2011

04:19

IA-64

Mpio.sys

6.1.7601.21720

353,152

04-May-2011

04:19

IA-64

Status

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

Additional file information

Additional file information for Windows Server 2008

Additional files for all supported x86-based versions of Windows Server 2008

File name

Update.mum

File version

Not Applicable

File size

3,078

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

X86_mpio.inf_31bf3856ad364e35_6.0.6001.22876_none_1d76d8f8a8a526ea.manifest

File version

Not Applicable

File size

1,659

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

X86_mpio.inf_31bf3856ad364e35_6.0.6002.22611_none_1f992adca59f52dc.manifest

File version

Not Applicable

File size

1,659

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

Additional files for all supported x64-based versions of Windows Server 2008

File name

Amd64_mpio.inf_31bf3856ad364e35_6.0.6001.22876_none_7995747c61029820.manifest

File version

Not Applicable

File size

1,661

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

Amd64_mpio.inf_31bf3856ad364e35_6.0.6002.22610_none_7bb6c6165dfdaabb.manifest

File version

Not Applicable

File size

1,661

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

3,102

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

Additional files for all supported IA-64-based versions of Windows Server 2008

File name

Ia64_mpio.inf_31bf3856ad364e35_6.0.6001.22876_none_1d787ceea8a32fe6.manifest

File version

Not Applicable

File size

1,660

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

Ia64_mpio.inf_31bf3856ad364e35_6.0.6002.22610_none_1f99ce88a59e4281.manifest

File version

Not Applicable

File size

1,660

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

2,257

Date (UTC)

12-Mar-2011

Time (UTC)

16:33

Platform

Not Applicable

Additional file information for Windows Server 2008 R2

Additional files for all supported x64-based versions of Windows Server 2008 R2

File name

Amd64_mpio.inf_31bf3856ad364e35_6.1.7600.20959_none_79d5e577c206e92b.manifest

File version

Not Applicable

File size

2,073

Date (UTC)

04-May-2011

Time (UTC)

06:02

Platform

Not Applicable

File name

Amd64_mpio.inf_31bf3856ad364e35_6.1.7601.21720_none_7bd3afa7bf1d1d35.manifest

File version

Not Applicable

File size

2,073

Date (UTC)

04-May-2011

Time (UTC)

05:56

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

3,170

Date (UTC)

04-May-2011

Time (UTC)

08:17

Platform

Not Applicable

Additional files for all supported IA-64-based versions of Windows Server 2008 R2

File name

Ia64_mpio.inf_31bf3856ad364e35_6.1.7600.20959_none_1db8edea09a780f1.manifest

File version

Not Applicable

File size

2,071

Date (UTC)

04-May-2011

Time (UTC)

05:58

Platform

Not Applicable

File name

Ia64_mpio.inf_31bf3856ad364e35_6.1.7601.21720_none_1fb6b81a06bdb4fb.manifest

File version

Not Applicable

File size

2,071

Date (UTC)

04-May-2011

Time (UTC)

05:46

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

1,933

Date (UTC)

04-May-2011

Time (UTC)

08:17

Platform

Not Applicable

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