If I were the OP, I would reconsider reconfiguring all the drives to RAID 1+0. Having the ability to recover my data after a media crash would be more important than the "potential" for better performance. Admittedly, it depends on the ultimate use of the system.

Doesn't matter how marginal the performance difference may be, the performance will be ZERO if a drive fails without some form of redundancy.

Nevertheless, a 1TB database on 4-drives is just asking for trouble. Drives are cheap !!! That's one thing that seems impossible to convince management of. In the long run, it would be cheaper to buy the hardware than it would to incur the labor costs and the inevitable data loss associated with restoring the system from a media failure.

As the saying goes, "Never enough money to do it right the FIRST time, but ALWAYS enough money to do it the SECOND, THIRD or FOURTH time."