1.) CAN you use a SSD & HDD in a RAID-0 array? Yes. SHOULD you? Definitely not.
2.) The capacity of a RAID-0 array is based upon the drive with the smallest capacity. So if you have a 128GB drive and a 500GB drive your array’s capacity will be 256GB (128 x 2), not 628GB.
3.) No, you do not get the speed of the SSD. Your array’s Read/Write speeds will be based upon the drive with the slowest Read/Write speeds, which is your HDD.
thanks bro good and clear!