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I thought I would come back here and report on a few things I found out, for the possible benefit of others.
This info is based on Dell Dimension E310 with RAID Level1 Intel option ROM and Intel Matrix Storage Manager.
Caveat utilitor. What I post here is based on my own findings with a sample of one. Back up your data, because YMMV.
- when the 2 disks are in a RAID Level 1 volume, they look like one disk *to Windows*. But if you boot to, say, Linux or DOS, you don't see the RAID volume, you see 2 disks.
- the 2 disks you see (in DOS or Linux) appear to be identical, including the MBR. The MBR can be read from each of the 2 disks using dd or Clonezilla (in Linux) or DSRfix (in DOS).
- in Linux, you can create a small text file on one of the disks, and it will *not* appear on the other disk. So you are truly looking at two separate disks. Warning: if you do this, it may screw up the RAID volume when you boot back to Windows.
- You can use the Intel option ROM (IOR for short) , or the Intel Matrix Storage Manager (IMSM for short) to separate the disks out of the RAID volume, and you will have two separate identical disks.
- You *can* put the disks back into a RAID volume without destroying the OS or the data *on the first drive*. Everything on the second drive (being added to the RAID volume) will be overwritten by what is on the first drive. To do this, you must use the IMSM, *not* the IOR.
My take-away from this long journey is as follows:
- set the system BIOS for RAID ON
- Separate the disks out of the RAID volume before working on them with any low-level tools which may not be RAID-aware. Physically unplug the second drive (which will act as a backup).
- When you've got the first drive cleaned up and working like a top, free of foistware and virus, use IMSM (*not* IOR) to put the disks together into a RAID volume. Make sure the first drive is the one you cleaned up, because when you join the 2 disks into a RAID volume with IMSM, it will copy (mirror) *everything* from the first disk to the other one, overwriting everything on the second drive. On a 75GB drive, this took about 30 minutes.
Again: this was my experience. YMMV, so backup all critical data before messing around with the drives.