Creating a RAID-0 array does not increase memory. It will increase the Read/Write performance.
A RAID-0 array's capacity is based upon the drive in the array with the smallest size.
So if your RAID-0 a 120GB drive and a 240GB drive your array's total capacity (before formatting) will be 240GB (120 x 2).
So if you RAID-0 those 2 drives you will be wasting 120GB of storage.
What RAID do i use then?