>> Can it be mounted and read as single JOBD or must it be mounted as >> a single unit of a mirror set in order to be read? > That should work if you mount it read-only. I would >avoid trying to write to it, or you could corrupt the RAID metadata.
Yeah, I figure that although its RAID 1, there will still be RAID related meta-data on the disk. I wondered if this meta-data made the disk unreadable. E.g. If you had one volume of a RAID5 set then you cant recover your data from it, but a volume of RAID 1 should be OK to recover data.
I also wondered if device names would cause conflicts. But, as you say, mounting it read only it should then be OK.
For scenarios 3 and 4, I was thinking along the lines that your desktop computer at work has RAID1 based USB drives for all your ~/home/ data. You just pull out the USB stick when you go home at the end of the day, and plug it in again in the morning. If the office burns down at night and you loose your computer, then your data is all on the USB stick and available to be read by another computer. This RAID1 approach may not be the best way to get yourself a backup, but would be one of the quickest / easiest to manage.
Maybe at a wlug meeting we could get Linux RAID1 up and running on a laptop with some USB sticks and subject it to some testing and see if it handles the abuse and how auto-magic it is, etc.