Striping is faster than mirroring as it writes for eg
if there are 10 pieces of data, it writes 1,3,5,7,9 to one and 2,4,6,8,10 to the other and this is faster than 1,2,3,4,5,6,7,8,9,10 to a drive.
hope this makes sense as its hard to explain -
STRIPING is for performance
MIRRORING is for backup