How do you duplicate a drive?

[Matt Staroscik]

I have a RAID mirror (2x 160GB) which I would like to back up onto a spare 
160GB drive.

I do not have a hot-swap caddy so I was planning on powering down the 
system to get the backup drive in and out.

But once I have the new blank drive in, what is the best way to duplicate 
the RAID? Ideally I would like to create a disk that could boot the system 
(and rebuild the RAID) in case disaster strikes.

Can dd do this?

I am new to Unix disk operations... Many thanks in advance for the help.