The G50V is capable of RAID-0 and RAID-1. You need 2 hard drives for either mode.
RAID-0 writes the info in stripes across the disks - for instance if your stripe size is set to 128k and you're copying a file that's 256k to the drives the first 128k is written to the first drive and the next 128k is written to the second drive. This makes sequential read speeds almost double that of a single drive. The drawback is that you need to keep good backups because if either one of your drives starts to develop problems the RAID-0 array is toast. You'll need to rebuild the array after replacing the bad drive and restore everything.
RAID-1 writes the data at the exact same place on both drives. It literally mirrors the drives. This is good for data security. If your first drive starts dying you can continue running on the second drive with no data loss until you replace the bad drive. There is no performance gain in RAID-1.