When you have two dynamic disks, and you create a mirror, the two disk are identical, except the second disk does not contain the boot files. Without the boot files it is not capable of starting Windows, so you have a choice of creating a boot floppy or copying the boot files to the disk so it will boot.
If you go into Disk Manager, if a mirror is in place, right click one of the drives and you see "break mirror". Click it
follow any instructions.
Once the mirror is "broken", you now have two separate disk. On the boot drive, general the c: drive, in the root directory of the drive (using explorer), you will see the files needed to boot Windows; the same Windows files needed to create a boot floppy, as described in the link.
From the c: drive, copy these files to the other disk of the broken mirror, to it's root directory. At this point you reinstate the mirror, let it sync up.
Now if lose the first disk of the mirror, and the server will not start, you switch the cable connector from the first disk to the second disk and the server should start.
If you have an SCA backplane, it is even easier, just requiring you to rotate the second disk to the first disk's slot.
The reason I use this method, no floppy required, no boot.ini editing, floppies die in a couple years, they get lost.
Now that I have you totally confused, you might just find it easier to create a boot floppy and edit the boot.ini to boot from the second drive.
To get back to the clone...
Once you have either the boot files copied or a boot floppy, the disk is a clone. You should make it boots as a single drive, as a test. I will refer to it as the "clone" from here on. Remove the "clone" from the machine.
Since at this point there have been no drive failures, the C: will boot. Make sure it does, shut down the machine.
Now if you want to maintain a mirror, plus have a cloned drive....
Obtain a new drive, mount the new drive in the same spot as the clone came from, attach data and power cables, start the machine. Go into Disk Manager and reestablish the mirror. The new disk will sync.
If you just need a clone, and not mirrored disks, put the clone away, start windows, go to disk manager, right click the remaining drive, choose "remove mirror"
The clone can now be placed in safe storage,
This whole procedure is confusing but really quite simple.
If I could write better, it would help
I highly recommend in the future to use a hot swap SCA backplane and a scsi or raid adapter capable of handling hot swapped drives.
It is so simple to create a clone from a raid 1 with the above mentioned hardware...
Pull 1 drive out of a slot, either one; the removed drive is a clone. Place it in safe storage. Place a new drive in the slot you removed the clone drive from. The newer adapters will sync up the mirror automatically. No need to create a boot file, copy files or go into Disk Manager. In 30 seconds you could be done.
Even better, if you have a raid 1 with a "hotspare drive", not need to pull the drive, just fail one of the raid 1 drives, the hotspare kicks in. This cuts down on the wear and tear on the SCA backplane/drive connectors, as they have an approx MTBF of 500 insertions.
Good night, I am beat.
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Chernobyl disaster..a must see pictorial