Replace RAID1 HDD [SOLVED]

[digitalmasters]

1) SATAII HDD installed in case at /dev/sda
2) SATAII HDD installed in case at /dev/sdb

They are both partitions exactly the same /boot swap /
I used the linux kernel to set them up in a RAID1 on the /boot and / partions.
The root partition is set up with LVM.
They are both up, fully functional, raid1 working.

I finally have the base gentoo system setup and I want to take the sdb drive out of the computer and store it as a backup.
Then install another SATAII HDD and set up the RAID1 again. so that I have drive failure protection.

How do I do it?
Do I need to break the raid, take the drive out, put another in, format/patition it, then re-establish the raid1?
How do I do that?

[quickshiftin]

how many sata drives can your computer run simulaneously?
if your box can run 3 drives, why not just replicate one of the existing drives onto your spare, and then just store that instead of replacing /dev/sdb.

as for the replication, you can copy the partition maps from an existing drive to the new drive using sfdisk
this from the gentoo-wiki