MPIO removes pseudo-LUN paths for external storage devices on Windows Server 2008 SP2-based servers or on Windows Server 2008 R2-based servers

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Symptoms

Consider the following scenario. On a server that runs Windows Server 2008 Service Pack 2 (SP2) or Windows Server 2008 R2, you have one or more external storage devices. For each storage device, there are one or more paths. You configure Microsoft Device Specific Module (MSDSM.sys) to discover multiple paths to external storage devices. When a failover event occurs, Microsoft Multipath I/O (MPIO) removes the disks or pseudo-logical unit numbers (LUNs) that represent the paths to a specific external storage device.

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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 Web site:

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

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

There are no prerequisites for installing this hotfix package.

Restart requirement

You must restart the computer after you apply this hotfix package.

Registry information

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

Hotfix replacement information

This hotfix does not replace a previously released hotfix package.

File information

The English (United States) version of this hotfix package uses a Microsoft Windows Installer package to install the hotfix package. The dates and the times for these files are listed in Coordinated Universal Time (UTC) in the following table. When you view the file information, the date 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 Server 2008 and Windows Server 2008 R2 file information

The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately. MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.