How do I configure dual fault-tolerant mirrored drives?

A. [Editor’s Note: Joshua Bolton submitted the following information.]

To configure dual fault-tolerant mirrored drives, you need two identical IDE drives. In the following example, I use IBM 14GB Deskstars. I set both drives to master and installed them in a Pentium motherboard on individual channels (i.e., IDE0 and IDE1).

Step 1:
Perform the hardware setup. Set the BIOS to auto for each drive, and boot the system. Make sure that the BIOS sees each drive. Turn off the server. Disconnect the cable from drive 0.

Step 2:
Boot on a DOS disk (e.g., DOS 6.22 or higher and one that contains FDISK and FORMAT). Create a 125MB primary partition, and format it with format c: /s so that it’s bootable. Reboot, and confirm that the partition boots.

Step 3:
Set your BIOS to boot the CD-ROM, or use a boot disk with CD-ROM drivers. Insert the Windows NT Server CD-ROM, and boot. Windows NT will use the 125MB DOS partition to load the setup files.

Step 4:
The installation program asks where you want to install NT and gives you the option of creating the partition. Create a 2GB temporary partition, and leave it as FAT. Install NT Server to this partition. Reboot and load NT. Install Service Pack 3 (SP3), but don’t install SP4 at this time. Reboot, and check the System Error log to make sure that everything is OK (i.e., no hardware errors about drives exist). Down the server, and turn it off. Reconnect the cable to IDE0, and repeat step 2 for this drive.

Step 5:
Boot NT Server. Open Disk Administrator, and create the extended partition on IDE0. The partition will be a 125MB DOS primary partition with the rest of the disk space, which is a 14GB logical partition in this example. Format the logical partition as NTFS. Down the server, and turn it off. Disconnect the cable from IDE1.

Step 6:
Repeat step 3, but when you get to step 4, install NT Server on the NTFS partition. Continue, and don’t do anything else. Complete the NT installation, and install SP3. Down the server, and turn off the system. Reconnect IDE1.

Step 6:
Start the system, which will boot to the first drive (i.e., IDE0). Open Disk Administrator, select IDE1, and delete the 2GB partition. From the menu, choose Partition and Commit Changes Now. Leave the logical partition on IDE1 as raw.

Step 7:
In Disk Administrator, highlight the NTFS partition on IDE0. Hold your control key, and select the same size logical partition on IDE1. Right-click, and select Mirror. From the menu, choose Partition and Commit Changes Now. The mirroring process will take some time and depends on how large your NTFS partition is.

Step 8:
Copy boot.ini from IDE0’s 125MB primary partition to IDE1’s 125MB primary partition.

Because the OS sets the BIOS to Auto for each drive and you set the BIOS to boot IDE first, if IDE0 fails, when you reboot your system, IDE1 will load NT Server with exactly IDE0’s contents because it’s a mirrored set. When you create the DOS primary partition and install NT Server to each drive, NT alters the partition table to look for the boot.ini (which is why you copy the final boot.ini to IDE1, as the drive partitions match). If a drive fails, you’ll be operational. You choose the time and place to reset the mirror. Always back up your system as a precaution.

To recover from a disk failure, you need a drive of exactly the same type as the one to replace as a spare. You should be able to use a different manufacturer’s drive, but I haven’t tested that theory. If IDE0 fails, move the drive on IDE1 to channel 0. Install the new drive on channel 1. If IDE1 fails, just replace the drive.

Your first step is to break the mirror set in Disk Administrator. Reboot when the program asks you to do so. After you reboot, confirm that the mirror set is gone. Down the server, and perform step 2 to set up the new drive. Bring up the server, and remirror the drive from IDE0.

I had serious problems with SP4 and dual processors during installation. SP3 let me create NTFS partitions larger than 4GB and was stable during the setup phase. Although Microsoft has released SP6, my production server has only SP5.