Booting From Mirror After Primary Partition Is Lost

If the partition containing the Windows NT Server system files is mirrored and then lost, you can use a fault tolerant boot floppy disk to restart Windows NT Server and access the mirror of the lost drive. This article explains how.

A fault tolerant boot floppy contains the files necessary to boot Windows NT from a mirrored partition. For instructions on creating a fault- tolerant boot floppy for x86-based systems and RISC-based systems, see the Concepts and Planning Guide for your version of Windows NT Server.

Once Windows NT is successfully booted from the fault tolerant boot floppy, the files and directories on the mirror drive are available for normal disk operations. Even if the disk containing the primary partition is lost, no differences are apparent to you (unless you study the status information displayed in Disk Administrator). But fault tolerance no longer exists: if the remaining partition is lost, all its data is lost also. So it is safer to break the current mirror set, configure a new boot and system partition, and create a new mirror.

Alternate Method of Creating a Fault Tolerant Boot Floppy

If the primary partition of a mirror set is lost, you cannot start Windows NT Advanced Server, and no other Windows NT system is available from which to create a fault tolerant boot floppy, follow these steps:

1. Boot to MS-DOS, either at another system or with a floppy on the current system.
2. Copy the Windows NT Advanced Server Setup Disk 1 for floppy disk installation to a blank floppy disk with the DISKCOPY utility (or another utility that will copy a mirror image of the original disk, including the boot sector).
3. Delete all files on the copied disk except NTDETECT.COM and NTLDR._.
4. Expand the NTLDR file to the SETUPLDR.BIN file using the command:
   
   EXPAND NTLDR SETUPLDR.BIN
   
   NOTE: To properly expand files from the Windows NT 3.51 or 4.0 CD-ROM, you must use the Expand.exe utility included with that version of Windows NT. The Expand.exe utilities included with Windows NT 3.51 and 4.0 can only be run from a command prompt in a 32-bit environment such as Microsoft Windows 95 or Windows NT.
5. If the mirrored drive is a SCSI disk requiring a SCSI driver to work with Windows NT, copy and expand the appropriate SCSI driver from the Windows NT Advanced Server Setup Disk 1, then rename it to NTBOOTDD.SYS.
6. Using a text editor such as EDIT.COM, create a BOOT.INI file with an ARC path that points to the Windows NT directory on the mirror partition.

The disk is now ready for use as a fault tolerant boot floppy.