Which of the following provides data the best fault tolerance at the LOWEST cost?

A.
Load balancing

B.
Clustering

C.
Server virtualization

D.
RAID 6

Explanation:
RAID, or redundant array of independent disks (RAID). RAID allows your existing servers to have
more than one hard drive so that if the main hard drive fails, the system keeps functioning. RAID
can achieve fault tolerance using software which can be done using the existing hardware and
software thus representing the lowest cost option.