Disk drive numbers may not correspond as expected to the SATA channel numbers when you install Windows on a computer that has multiple SATA or RAID disks

Article ID: 937251 - View products that this article applies to.
Support for Windows Vista Service Pack 1 (SP1) ended on July 12, 2011. To continue receiving security updates for Windows Vista, make sure that you're running Windows Vista with Service Pack 2 (SP2). For more information, refer to this Microsoft webpage: Support is ending for some versions of Windows
(http://windows.microsoft.com/en-us/windows/help/end-support-windows-xp-sp2-windows-vista-without-service-packs)
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Symptoms

Consider the following scenario:
  • You have a computer that is running on one of the following operating systems:
    • Windows Server 2012
    • Windows Server 2008 R2
    • Windows Server 2008
    • Windows 8
    • Windows 7
    • Windows Vista
  • You add two Serial Advanced Technology Attachment (SATA) or RAID hard disks to the computer.
  • The SATA or RAID hard disks are attached to channels 0 and 1.
In this scenario, Disk 0 may not be assigned to the hard disk on channel 0, and Disk 1 may not be assigned to the hard disk on channel 1. You expect the disk assignment numbers to match the corresponding SATA or RAID channel numbers.

Note You may experience this problem if you configure the operating system during installation or if you perform a recovery process that was provided by the computer manufacturer. This problem can also occur during regular operating system startup. Therefore, hard disks may have different disk numbers across multiple system startups. Also, drives may enumerate in different orders if the operating mode of the hard disk controller is changed in the BIOS (for example, RAID mode versus non-RAID mode).
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Cause

The disk-assignment numbers may not necessarily match the corresponding SATA or RAID channel numbers. There is no assurance of a consistent relationship between PnP enumeration and the order of the hard disks that are detected during startup. Devices are presented in the order in which they are enumerated. Therefore, the disk assignment numbers may change between startups. For example, assume that you run Windows or Windows Server Setup on a computer that has two unformatted SATA or RAID hard disks. In this situation, Windows may present the second hard disk as Disk 0 when you are prompted for the disk on which to install the operating system.
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Resolution

When you set up any of the operating systems that are listed in the "Symptoms" section on a computer that has multiple SATA or RAID hard disks, verify the disk drive on which you will set up the system by checking the disk information. For example, on the screen that lets you select the drive for the setup destination, verify the volume name and the available space.

To see the assigned disk numbers, use any of the following methods:
  • Run the Disk Management console. To do this, click Start
    Collapse this imageExpand this image
    Start button
    , type diskmgmt.msc in the Start Search box, and then click diskmgmt.msc in the Programs list.
  • Use the Diskpart.exe command-line utility to run the list disk command.
  • During Windows or Windows Server Setup, the assigned disk numbers are listed when you are prompted to select a drive and a partition for the installation.
Note Under certain circumstances, it may be difficult to notice that the disk numbering does not match the corresponding SATA or RAID channel numbers. For example, if both the SATA or RAID hard disk sizes are identical, it may be difficult to determine the identity of the disks by using these methods.
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More information

When you set up one of the operating systems that are listed in the "Symptoms" section on a computer that has multiple hard disks, you expect the disk assignment numbers to match the corresponding SATA or RAID channel numbers. If you experience mismatched channel assignments, you may set up the operating system on the wrong drive, or you may try to format the incorrect drive partition. Therefore, you may lose important data.

Additionally, when you install Windows Server 2012, Windows Server 2008 R2, Windows 8, or Windows 7, the installation creates a system partition alongside the Windows partition by default. The system partition is created to accommodate a Bitlocker requirement. Bitlocker requires that the boot files and Windows files are located on separate partitions. If the preselected default hard disk is not changed, the system partition is created on the disk that is detected as Disk 0.
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Status

Microsoft has confirmed that this problem is due to design limitations in the Microsoft products that are listed in the "Applies to" section. This problem occurs because drives are enumerated in the order in which they are presented to the operation system by the system BIOS.
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References

For more information about a related issue, click the following article number to view the article in the Microsoft Knowledge Base:
937252
(http://support.microsoft.com/kb/937252/ )
Volume numbers in the "Volume ###" column may change every time that you run the "List Volume" command in the Diskpart.exe utility in Windows
For more information about PnP enumeration and hard disk drive letter assignments in Windows Server 2003 and Windows XP, click the following article number to view the article in the Microsoft Knowledge Base:
825668
(http://support.microsoft.com/kb/825668/ )
Overview of PNP enumeration and hard disk drive letter assignments in Windows Server 2003 and Windows XP
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Properties

Article ID: 937251 - Last Review: February 15, 2013 - Revision: 6.0
Applies to
  • Windows Server 2012 Datacenter
  • Windows Server 2012 Essentials
  • Windows Server 2012 Standard
  • Windows Server 2008 R2 Enterprise
  • Windows Server 2008 R2 Datacenter
  • Windows Server 2008 R2 Standard
  • Windows Server 2008 Enterprise
  • Windows Server 2008 Datacenter
  • Windows Server 2008 Standard
  • Windows 8 Enterprise
  • Windows 8 Pro
  • Windows 8
  • Windows 7 Enterprise
  • Windows 7 Ultimate
  • Windows 7 Professional
  • Windows 7 Home Premium
  • Windows 7 Home Basic
  • Windows Vista Enterprise
  • Windows Vista Ultimate
  • Windows Vista Business
  • Windows Vista Home Premium
  • Windows Vista Home Basic
Keywords: 
kbtshoot kbprb kbexpertiseinter KB937251
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