Using Emergency Repair Disk With Fault Tolerant Partitions

After creating volume sets, stripe sets with parity, stripe sets without parity, or mirror sets, always save the disk configuration information to the Windows NT Emergency Repair Disk. Running the Emergency Repair Disk without updated disk configuration information may make some partitions inaccessible, or make it impossible to start Windows NT.

During Windows NT installation, an Emergency Repair Disk is created that includes the System Registry hive. This contains a Disk subkey that stores information about disk partitions as they existed during setup. As new disk partitions are created and existing partitions deleted, the Disk subkey is updated. Therefore, the Disk subkey on the Emergency Repair Disk should also be updated.

Information stored in the Disk subkey includes the number of partitions on each disk, the signature number of the disk, and additional information on each partition in the disk such as:

• the type of fault tolerant volume the partition is a member of
• the current fault tolerant state (such as "Healthy")
• the relationship of the partition in the fault tolerant volume (for example, in a mirror set the primary partition is identified as logical partition number one, and the mirror partition as logical partition number two)
• which fault tolerant set the partition is a member of.

If the disk configuration is saved in Disk Administrator, it is available to you if you later have to restore it or to be used with the Emergency Repair Disk when repairing a damaged Windows NT system.

If disk configuration information has not been saved to the Emergency Repair Disk, and you run the Disk and restore the default system hive, Windows NT and Windows NT Advanced Server will not recognize volumes such as stripe sets (with or without parity), volume sets, and mirror sets of partitions other than the boot or system partition. Disk Administrator will show them as being "single" primary or extended partitions with an unknown file system type. Although the partitions are intact, Windows NT cannot identify their volume or partition type.

When the boot and system partitions are mirrored, running the Emergency Repair Disk without the updated disk configuration information may result in this error message at the autocheck screen when you try to start Windows NT: