November 6th, 2009      click here view more articles

The disk is not accessible. The disk may have experienced hardware failure, corruption, or I/O errors. The disk's copy of the system's disk configuration database may be corrupted. An error icon appears on the Unreadable disk. Both dynamic and basic disks display the Unreadable status.
Disks may display the Unreadable status while they are spinning up or when Array Manager is rescanning all of the disks on the system. In some cases, an Unreadable dynamic disk has failed and is not recoverable. For dynamic disks, the Unreadable status usually results from corruption or I/O errors on part of the disk, rather than failure of the entire disk as follows.

The following are some instances:
Example 1:
I had reason to re-install windows onto my system drive. Before I did that I checked to make sure that the data drive, which is formatted as an NTFS drive, and is a dynamic disk, was intact and functioning fine.

With XP installed on the system drive I went to look for the data drive in explorer (have done this procedure on many occasions without problems) and could not see the drive. Go to administrative tools and I see a message that says the drive is Unreadable Dynamic Disk. I have scanned the drive with maxtor tools and it has absolutely no errors on it whatsoever.

I have tried using a number of data recovery tools but as they can't see the drive, I can't do anything here. If I type diskpart in CMD the drive is listed but, again, can't do anything with it.

Example 2:
Because my motherboard is spoiled and so changed a new motherboard. I have 2 hardisk, so the hardisk with window I formatted, after i logon to window my another disk it show "Unreadable Dynamic Disk" in the disk management.

How to fix Unreadable Dynamic Disk by using Dynamic Disk Converter 3.0?

In fact, some of them solved this problem after use the solution that gave by Microsoft, but some of them still stay in that trouble. They search "how to fix dynamic disk unreadable?" on google, the finally format the unreadable dynamic disk, and they lost all data in it. Fortunately, Dynamic Disk Converter 3.0 can revert a unreadable disk to basic disk to fix WITH NO LOSS OF DATA, even if the dynamic disk can not be accessed.

Fix Unreadable Dynamic Disk Steps

1. Select your unreadable dynamic disk that you want to fix to basic disk.
2. For data security, if any data will be lost during the repairing, you will be prompted by the program.
3. Confirm that the selected disk which you wish to repair.
4. Executing...Report of the fix is complete,
5. After completing, you need restart the computer to take effect, and then the disk becomes readable!

The following is a screen shot:

For more information: Dynamic Disk Converter 3.0

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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.

More information at: http://support.microsoft.com/kb/236086