gmirror setup

[Jonathan Horne]

i just set up my first gmirror raid1, and... it was really simple.  too 
simple.  "ok... what did i skip or do wrong?", was my first thought.

i follow the doc from onlamp.com:

http://www.onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html?page=1

i did have one giant deviation tho, and im wondering if it really makes a 
difference.  the article depicts creating the gmirror immediately following 
initial operating system install, but i did my example on a fully functioning 
system.  other than that, i have 2 identical disks, and things seem to be 
working:

castor# gmirror status
      Name    Status  Components
mirror/gm0  DEGRADED  ad0
                      ad1 (33%)

im sure im seeing less than the best performance since im using but a single 
ide channel, but other than that, is it feasible to insert an identical disk, 
and setup the gmirror at anytime a freebsd'er likes?

also, the doc didnt mention it, but if you do use to differing disk sizes, 
obviously the smaller one should be ad0?  and other than that, is there any 
difference in setting up gmirror if the second disk is larger?

cheers,
jonathan