Encrypted zfs?

Hello list,

I'm currently using a zraid consisting of three drives. Lately I wonder 
what the best way would be to encrypt it.
I read the chapter dealing with disk encryption in the handbook, and 
decided to use GELI. Is there anyone here on the list who has some 
experiences with ZFS on encrypted GELI devices? Are there some 
performance specs around?

And what is even more important: What is the best of moving the zraid to 
encrypted devices?
I can't remove one of the disks because they are in use. So I figure one 
way would be to buy another disk, set up encryption and add it to the 
pool. I could then remove one disk after the other, encrypt it, remove 
the (now broken one) from the zpool, and add the newly encrypted device.
Since buying disks costs money I wonder how save it would be to follow 
this procedure without adding a new disk. From my point of view I'll 
loose redundancy as soon as I remove one of the three disks. But is 
there another problem or something dangerous I don't see her?

Regards
Christian