[CentOS] RAID configuration suggestion???

we have several DELL R900 with PERC 6/E adapter in it. R900 using Redhat Linux. Each R900 have two PERC 6/E adapter and at least two MD1000 connect to it.

Configuration 1:

PERC 6/E -- two MD1000 PERC 6/E -- empty

Configuration 2:

PERC 6/E -- MD1000 PERC 6/E -- MD1000

Normally first MD1000 for database and second MD1000 for nightly backup. My co-worker told me there is NO difference on performance or battery life on botn configurations.

I would like listen to your opinion on follwoing:

1. which configuration have better performance?

2. put two MD1000 on same PERC 6/E adapter will cause battery life shorter?

3. other comment?

Thanks.