Symptoms

Consider the following scenario:

  • You have Hyper-V virtual machines (VM) that are configured on Windows Server 2012 Hyper-V Cluster by using Scale Out File Server as the Storage Solution.

  • The virtual machine .vhdx files are held in Cluster Shared Volume (CSV).

  • CSV Block Cache is enabled on the volume.

In this scenario, virtual machines may experience slow performance.

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 this specific problem.

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, submit a request to 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 2012.

Registry information

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

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

The global version of this hotfix installs files that have the attributes 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 2012 file information notesImportant Windows Server 2012 hotfixes are included in the same Windows 8 hotfix packages. However, only Windows 8 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 8". Always refer to the "Applies To" section in an article 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

    6.2.920 0.20 xxx

    Windows Server 2012

    RTM

    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 2012" section. MUM, MANIFEST, and the associated security catalog (.cat) files, are very 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 2012

File name

File version

File size

Date

Time

Platform

Csvfs.sys

6.2.9200.20927

626,176

27-Jan-2014

04:34

x64

Csvvbus.sys

6.2.9200.20927

152,576

27-Jan-2014

04:33

x64



Status

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

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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 Note The following PowerShell command may be used to view if CSV block cache is enabled or not on a particular CSV volume:

PS C:\temp> Get-ClusterSharedVolume “OS_0002” | Get-ClusterParameter CsvEnableBlockCache

Object Name Value Type
------ ---- ----- ----
OS_0002 CsvEnableBlockCache 1 UInt32

Additional file information for Windows Server 2012

Additional files for all supported x64-based versions of Windows Server 2012

File property

Value

File name

Amd64_013f3fed0f4a486f32a984d3fc5c9633_31bf3856ad364e35_6.2.9200.20927_none_ce3382053eccd103.manifest

File version

Not applicable

File size

718

Date (UTC)

27-Jan-2014

Time (UTC)

13:22

SHA-1 hash

Not applicable

MD5 hash

Not applicable

File name

Amd64_microsoft-windows-f..rcluster-csvfs-core_31bf3856ad364e35_6.2.9200.20927_none_2fce0453021c3425.manifest

File version

Not applicable

File size

3,087

Date (UTC)

27-Jan-2014

Time (UTC)

06:24

SHA-1 hash

Not applicable

MD5 hash

Not applicable

File name

Amd64_vbus.inf_31bf3856ad364e35_6.2.9200.20927_none_1fe91da4f9e04882.manifest

File version

Not applicable

File size

2,096

Date (UTC)

27-Jan-2014

Time (UTC)

06:24

SHA-1 hash

Not applicable

MD5 hash

Not applicable




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