You have to "Reconfigure" your 2-disk RAID 1 to a single-disk RAID 0.  Once you have done that, then you need to create a new single-disk RAID 0 using the second disk.  Just keep in mind that without RAID 1, you will have NO redundancy - just like a desktop PC, if the disk dies/fails, you will lose it all (in RAID 1, if one disk dies/fails, it will keep running on the remaining disk). You will need to do this in OpenManage Server Administrator (OMSA) - available on the disks that came with your server and/or downloadable from support.dell.com. If you cannot reconfigure a 2-disk RAID 1 to a single-disk RAID 0, then you will need to simply delete the RAID 1 in the CTRL-R BIOS utility, configure the first disk as a single-disk RAID 0, install the OS, use OMSA to configure the second disk as a single-disk RAID 0.
Dear All, I bought a brand new Dell R710(PERC 6/i) which is loaded with windows 2008 R2.Machine having two 300 GB hard disk which are configured as Raid 1.I would like to use the second disk as data storage.Can anyone please help me to explain how to remove Raid 1 configuration and use the disk as independent without any mirroring.I dont have any data on hard drive other than OS as I said it is a bran new machine.  Thanks & Regards Aneesh Joseph
How to remove Raid 1 config in Dell R710 PERC 6/i Integrated