This is a branch off of Q_21482564.html "Migrate from software mirror to Promise RAID?" See my post-mortem notes there.
Now looking for a RAID card, more elaborate than the Promise card I bought, that allows one to run surface diagnostics, for example Microsoft "chkdsk /r" on each individual surface without having to tear apart the RAID controller and cabling to the disks.
With the Promise card I have it is uncertain exactly what chkdsk does. With the Microsoft mirror system, I learned that chkdsk tests only the disk0 surface (of the disk0 + disk1 mirror). Results and faulty conclusions abound in a very sucky situation.
I would call this feature something like, "pass-through surface testing". That is, the RAID card would manipulate specifically 1 of the disks in the array and test it, then switch to another disk, etc.