System or Boot Disk Listed as Dynamic Unreadable in Disk Management

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Article ID: 236086 - View products that this article applies to.
This article was previously published under Q236086
Notice
This article applies to Windows 2000. Support for Windows 2000 ends on July 13, 2010. The Windows 2000 End-of-Support Solution Center is a starting point for planning your migration strategy from Windows 2000. For more information see the Microsoft Support Lifecycle Policy.
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SYMPTOMS

When you view your system disk or boot disk in the Disk Management tool, it may be listed as "dynamic unreadable", and you may be unable to use the Disk Management tool to manage this disk. Note that this behavior may occur even though the operating system is currently running from your system disk or boot disk. Your original dynamic system disk or boot disk may now be listed as "Missing" - "Offline", and all volumes contained on the missing disk are noted as "failed" and are not accessible. If you then try to reactivate the missing disk, you may receive the following error message:
The specified disk could not be located.
Also, the System Event log may contain entries for each "failed" volume contained on the missing dynamic disk:

Event ID: 3
Event Source: dmboot
Description: dmboot: Failed to start volume Sysdrive (C:)

CAUSE

This problem can occur if Windows 2000 was re-installed and during Setup a volume on the dynamic disk was deleted and recreated, or another disk partitioning tool like Fdisk was used to create a new partition. Windows 2000 Setup and other disk partitioning tools can only create basic partitions. Creating any partitions on a dynamic disk outside of Windows 2000 or during Setup creates a disk with both dynamic and basic partition table entries. Re-creating a volume during Windows 2000 Setup changes the partition system-id byte from type 0x42 (dynamic) to a basic partition system-id byte based on the file system chosen, usually 0x06 for FAT, 0x0B for FAT32 or 0x07 for NTFS. Anytime there is a mix of basic and dynamic system-ID bytes, the disk will be viewed as Dynamic Unreadable in Disk Management.

RESOLUTION

WARNING: Do not delete any of the missing or offline dynamic disk volumes, especially if they were part of a spanned, striped, or a Raid-5 volume. Doing so could lead to permanent data loss.

NOTE: The following procedure may make your computer unbootable or it may stop during startup with a "STOP 0x0000006F SESSION3_INITIALIZATION_FAILED" error message if the associated LDM database that contains the original partitioning scheme does not agree with the partitioning scheme that was created when Windows 2000 was reinstalled. You should perform a system backup prior to following this procedure.

To work around this problem, use a disk editing tool (such as DiskProbe) and save a copy of the master boot record (sector-0 of the physical disk) to a floppy disk, and then change the incorrect system or boot partition system-ID back to a type 0x42. Next run Regedt32 and ensure the following three services have a Start value of zero:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dmboot Start:REG_DWORD:0

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dmio Start:REG_DWORD:0

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dmload Start:REG_DWORD:0
After you make these manual repairs, if the computer starts successfully, the dynamic disk should be recognized and associated volumes should become accessible again.

If the system will not boot after making the changes, you can use the Microsoft Windows NT Resource Kit Disksave.exe utility to restore the original master boot record (MBR) sector that you saved before making the change.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

MORE INFORMATION

227364 Dynamic Volumes Are Not Displayed Accurately in Text-Mode Setup
Information about Dskprobe, partition tables and system-IDs are detailed in the Windows 2000 Resource Kit. Dskprobe can also be found on the Windows 2000 CD-ROM in the Support\Tools folder.

Properties

Article ID: 236086 - Last Review: February 26, 2007 - Revision: 3.4
APPLIES TO
  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Datacenter Server
Keywords: 
kbprb kbui KB236086

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