lvm on raid1 for a backup server or not?

[Zhengquan Zhang <zhang.zhengquan@gmail.com>]

Dear debian community,

I will build up a backup server which has 2x1T + 1x250G drives. the size
of the one full backup will be about 400G.

My initial plan was to install debian lenny on the 250G drive. leave
2x1T drive untouched and then make software raid1 on them after the
installation. 

I have a few questions that I have not figured out the answer after
googling. 

1. Is it advised to install the system on the 250G drive as well as the
2x1T drive? Installing the system on 3 drives will enable the machine to
boot if the 250G drive fails. But in that case, will the machine boot
correctly using system installed on the 1T drive? and How can I directly
install the OS on 3 drives simultaneously?

2. I have used lvm on other systems but not on raid. I wonder if it is
advisable to use lvm over raid on a backup server. The rationale of LVM
is to make resizing easier but in this situation is it advisded to use
LVM on the raid1 array and the 250G boot drive?

Thanks for any pointers,

-- 
Zhengquan