raidctl -B syntax

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

I'm unsure what the "dev" argument to raidctl -B is: the spare or the original?

Suppose I have a level 1 RAID with components A and B; B failed. I add C as a 
hot spare (raidctl -a C) and reconstruct on it (raidctl -F B) now I have A 
"optimal", B "spared" and C "used_spare".
Then I find that B's failure must have been a glitch; do I raidctl -B B or 
raidctl -B C?
I suppose that after the copyback, I'll have A and B "optimal" and C "spare", 
right?
What if, during the reconstruction, I get an I/O error on B. I hope the 
reconstruction will simply stop and leave me with A "optimal", B "spared" and 
C "used_spare", right?