gmirror: replacing a drive with a bigger one.

[Dennis Berger]

Hi,
currently I have two 180gb drives in a RAID1 with gmirror. Now we need 
to extend the size so I would like to replace both drives with 500gb drives.
Is there a recommend way to do this?
I suggested replacing one drive at first and let gmirror set it up to as 
a 180gb. Then use growfs to extend the last partition this is my /data 
partition.
Or should I use dump/restore and dd to replace? What do I have to keep 
in mind then? copying metadata and such?
What do you suggest?
Thanks,
Dennis