Symptoms

When you use a back-end storage area network (SAN) on a computer that is running Windows Server 2008 R2, the disk write performance is slow. Specifically, the disk write performance is slower than if you use the same back-end SAN on a Windows Server 2003-based computer.

Cause

This issue occurs because deferred procedure calls (DPCs) are given an incorrect priority when they are queued.

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 Windows Server 2008 R2 Service Pack 1 (SP1).For more information about how to obtain a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

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

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.

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

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, 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

    Milestone

    Service branch

    6.1.760 1.22xxx

    Windows Server 2008 R2

    SP1

    LDR

  • GDR service branches contain only those fixes that are widely released to address widespread, critical 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 maintaining the state of the updated component. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

File name

File version

File size

Date

Time

Platform

Storport.sys

6.1.7601.22133

190,856

12-Oct-2012

18:27

x64

File name

File version

File size

Date

Time

Platform

Storport.sys

6.1.7601.22133

430,448

12-Oct-2012

18:05

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:

824684Description of the standard terminology that is used to describe Microsoft software updates

Additional file information

Additional file information for Windows Server 2008 R2

File name

Amd64_27b8940c0d978b607908def12d73a0bd_31bf3856ad364e35_6.1.7601.22133_none_185c4ebfb10929a1.manifest

File version

Not applicable

File size

700

Date (UTC)

15-Oct-2012

Time (UTC)

07:32

Platform

Not applicable

File name

Amd64_microsoft-windows-storport_31bf3856ad364e35_6.1.7601.22133_none_8615307b5ffd5647.manifest

File version

Not applicable

File size

15,727

Date (UTC)

13-Oct-2012

Time (UTC)

00:38

Platform

Not applicable

File name

Ia64_f1f0ab003b15ef44bfb351a4665ec87c_31bf3856ad364e35_6.1.7601.22133_none_6a612236cda7e412.manifest

File version

Not applicable

File size

698

Date (UTC)

15-Oct-2012

Time (UTC)

07:32

Platform

Not applicable

File name

Ia64_microsoft-windows-storport_31bf3856ad364e35_6.1.7601.22133_none_29f838eda79dee0d.manifest

File version

Not applicable

File size

15,726

Date (UTC)

12-Oct-2012

Time (UTC)

19:29

Platform

Not applicable

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