What is the need for having FALLBACK option during creating Tables when we have RAID-1 which has a mirror copy of a disk.doesnt it add overhead and cost?
Fallback does add overhead and cost. The value is an additional level of protection. If an AMP goes offline for some reason, a fallback-protected table is still accessible. Fallback also provides a means of recovery from data corruption due to software or CPU faults that RAID controllers cannot detect.