A boot LUN can be disabled if it is claimed for use with MPIO in Windows Server 2008 R2

Consider the following scenario:

• You configure a Windows Server 2008 R2-based computer to start from a logical unit number (LUN) that is created on a storage area network (SAN).
• You configure the page file to be located on another disk instead of on the boot LUN.
  Note The disk that stores the page file must be attached to a controller other than the boot controller.
• You install the Multipath IO (MPIO) feature on the computer.
• You use a device-specific module (DSM) to claim the LUN for use with MPIO.
• You restart the computer.

In this scenario, you can disable the boot LUN in Device Manager. However, the expected behavior is that the option to disable the boot LUN should always be unavailable.

Notes

• If the boot LUN is disabled by any application or service, you may experience various Stop error messages, for example a "0x0000007B" Stop error message. Additionally, you may also experience data loss because of these Stop errors.
• This issue may be triggered when you apply maintenance to a Storport miniport or to the Storport.sys driver.

This issue occurs because the MPIO driver (Mpio.sys) incorrectly handles the request to mark the boot LUN as "cannot be disabled."

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, go to 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.

Prerequisites

To apply this hotfix, you must be running Windows Server 2008 R2 or Windows Server 2008 R2 Service Pack 1 (SP1). For more information about how to obtain Windows Server 2008 R2 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

Registry information

To use the hotfix in this package, 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.

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 R2 file information notes

• 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 0.16xxx	Windows Server 2008 R2	RTM	GDR
  6.1.760 0.21xxx	Windows Server 2008 R2	RTM	LDR
  6.1.760 1.17xxx	Windows Server 2008 R2	SP1	GDR
  6.1.760 1.21xxx	Windows Server 2008 R2	SP1	LDR

• GDR service branches contain only those fixes that are widely released to address widespread, extremely important issues. LDR service branches contain hotfixes in addition to widely released fixes.
• 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

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

To work around this issue, configure the page file to be located on the boot LUN.

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

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

Additional file information

Additional file information for Windows Server 2008 R2

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

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