[lug] upgrading OS on RAID1

[durist at frii.com]

I've just ordered a second IDE hard drive for my home machine (AMD/Debian) 
which I'm planning to use as an OS mirror. Aside from adding hardware 
redundancy, I wanted to do this so I could break the mirror, upgrade one side 
and test it, and then revert to the other mirror if something goes wrong 
(especially since my wife uses this machine for work and she's currently 
paying the bills). This has become more or less standard operating procedure 
for Sun/Solaris production systems, and it's made relatively easy by putting 
in device aliases for the boot devices in the Sun's NVRAM. This sadly is a 
feature that Intel boxen don't have. I was curious if other people routinely 
do this split-mirror/upgrade/test/sync-mirror procedure on intel, and what 
pitfalls there might be (other than the obvious dangerous confusion over 
which disk is which at 3am-- in my Solaris experience this is the sort of 
procedure you want an explicit checklist for). I've googled around, and I 
haven't seen any mention of this as one of the advantages of doing software 
RAID 1 on linux, which seems odd.