[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.