An update that improves the compatibility of Windows 7 and Windows Server 2008 R2 with Advanced Format Disks is available

Applies to: Windows 7 EnterpriseWindows 7 Home BasicWindows 7 Home Premium


This article describes an update that improves the compatibility of Windows 7 and Windows Server 2008 R2 with Advanced Format Disks that have a 4KB physical sector size. This hotfix is only applicable to Advanced Format disks which report themselves as having a 4 KB physical sector size, and which emulate a logical addressing interface of 512 bytes.

Note Advanced Format disks introduce a larger physical sector (4 KB). However, to make initial versions more compatible with current computer systems, they maintain a 512 byte logical addressing interface. Therefore, they are known as “512-byte emulation disks,” or “512e” for short. For more information about Advanced Format disks, please visit the International Disk Drive Equipment and Materials Association (IDEMA) website that is listed at the end of this article.


Hard disk drives have traditionally been based on 512 byte sectors, and all access to the physical media was addressed based on this unit. Recently, hard disks vendors have begun to transition to new disks that have a sector size of 4096 bytes (4 KB). These are generally known as an “Advanced Format Disk.” Because disks are only able to perform physical media updates in the granularity of the physical sector (4 KB in this case), a 512 byte write that is directed to the disk will require some additional work in order to be completed. This work comes at the cost of performance and reliability, with the specific cost varying based on the workload and hardware implementation. To avoid this additional work, applications must be updated to natively support writes that are based on the 4 KB sector granularity.

This KB article introduces new storage infrastructure to support querying for the physical sector size of the storage device. Additionally, this KB article introduces support in certain key system components for these kinds of disks in order to improve performance, reliability, and general interoperability.

A more detailed technical discussion into the special considerations developers have to take with these kinds of disks are out of the scope of this KB article and will be detailed in a companion document on MSDN.

Issues that this hotfix rollup package fixes

This hotfix rollup package resolves the following issues that were not previously documented in a Microsoft Knowledge Base article. Any of these following issues can be encountered when you use an Advanced Format disk.

Issue 1 You receive an error message when you click the Check for Updates button on Windows Update site

    Issue 2 An Issue Occurs when many small writes are performed

    Issue 3 Applications cannot query the physical sector size of an external storage device

    Issue 4 Applications cannot query the physical sector size of a storage device

    Issue 5 Storage drivers do not support correct sector size reporting for Advanced Format disks

    Issue 6 Fsutil.exe tool issue


    Update information

    How to obtain this update

    If you are not sure which Windows version is installed, follow these steps:

    1. Click Start, type msinfo32 in the Start Search or Search programs and files, then press ENTER.
    2. Locate your operating system next to the OS Name line and your architecture type next to the System Type line.

    The following files are available for download from the Microsoft Download Center:

    Operating system Update
    All supported x86-based versions of Windows 7 Download Download the update package now.
    All supported x64-based versions of Windows 7 Download Download the update package now.
    All supported x64-based versions of Windows Server 2008 R2 Download Download the update package now.

    For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:

    119591 How to obtain Microsoft support files from online services

    Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.


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

    • Windows 7
    • Windows 7 Service Pack 1 (SP1)
    • Windows Server 2008 R2
    • Windows Server 2008 R2 Service Pack 1 (SP1)

    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

    Restart requirement

    You must restart the computer after you apply this hotfix.

    Update replacement information

    This update does not replace a previously released update.

    File information


    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

    Microsoft has added sample code to the WDK which provides details about how developers can extract the reported storage access alignment information from the STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR structure when you make a call to the IOCTL_STORAGE_QUERY_PROPERTY control code:

    Although Microsoft has taken steps to improve support for Advanced Format disks which run alongside Windows 7 and Windows Server 2008 R2, it is up to software developers to update their applications . It is observed to be the general trend of the Storage Industry to transition to larger sector sizes over the coming years, and applications must make sure that they are ready for this transition. Microsoft is preparing additional MSDN and TechNet documentation which will educate Developers and IT Pros as to the special considerations which have to be taken to support Advanced Format disks. The following table details Microsoft supports for different hard disk formats.

    Support for Hard Disk Formats based on OS Version
    Common Name(s)Physical sector sizeLogical sector sizeWindows Version with Support
    Legacy 512 Native, 512 Native, Legacy 512 bytes512 bytesAll Windows versions
    Advanced Format, 512-bye Emulation, 512e, 4k/512e4 KB512 bytesWindows 7 with MS KB 982018
    Windows 7 SP1
    Windows Server 2008 R2 with MS KB 982018
    Windows Server 2008 R2 SP1
    4K Native, 4k/4k4 KB4 KBNot supported as of Windows 7 SP1 or Windows Server 2008 R2 SP1. Microsoft is conducting an investigation into the feasibility of supporting these kinds of disks in the future and will issue the necessary KB articles when it is appropriate.
    OtherNot 4 KB or 512 bytes.Not 4 KB or 512 bytes.Not supported
    Note Support for Advanced Format disks relies on the disk reporting itself as having 4KB physical sectors, and relies on the Storage Driver reporting the physical sector size.

    For more information, visit the following websites: For more information on Advanced Format Disks, visit the following IDEMA website: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.