I've sent an email to the list, showing the graphs (i think it is waiting for approval)
In the meantime...
I'm able to change to any of this below, if it will improve my performance:
Replace existing 4x3TB Disk with 1.5TB Silver SAN
Replace existing 4x3TB Disk with 4x800GB SSD Drives (Raid 5)
Replace existing 4x3TB Disk with 8x600GB 15K SAS (Raid 10)
Add 4x3TB to existing Raid 10