RAIDframe component replacement

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I would need some advice on RAIDframe failing component replacement (on 
4.0.1/amd64).

I have a RAID1 consisting of sd0a and sd1a. Now, sd0 sometimes fails with 
"hardware error", but reconstruction onto it is OK. Of course, I want to 
replace the disc. Luckily, I have a spare drive and everything is hotpluggable 
SCA and I have unused slots.

It seem I have two options (given the spare disc I have has already been 
fdisk'ed and disklabel'ed):
1. Leave the two current discs in, insert the replacement disc, scscictl scan 
it (becoming sd2) and then add it as a hot spare via raidctl -a sd2a, Then, 
raidctl -F sd0a which should begin a reconstruction on sd2a.
2. Do a raidctl -f sd0a (if sd0 hasn't been marked as failed already), then 
scsictl detach it and pull it out. Then, substitute it with the replacement 
disc, scsictl scan (does it become sd0 then?) and raidctl -a sd0a. Probably I 
have to raidctl -F component0 again in order for the reconstruction to begin.

What's the preferred method?
I would like to end up with a setup that is bootable again (given I 
installboot'ed on the spare). Also, the configuration preferably should look 
unchanged (i.e. sd0a/sd1a and not component0/sd1a/sd2a).
Additionally, I would prefer the procedure that is safer against the remaining 
component (sd1) failing in the middle of it.

Thanks for your help.