Try to use hdparm to set your hard-drive in read-only mode.
Interesting suggestion, certainly shouldn't hurt. But AFAIK the device mapper runs in the kernel and it's going to do it's "own thing" before I get a chance to hdparm it.
That's why I'm most interested in determining what (if anything) a LVM configuration does ... especially in situations where it detects a bad/repairable configuration (if that even makes sense).
Regardless, I'll do some experimenting - not sure if there are going to be any limitations with hdparm and configuring my disks via a USB adapter.