RAID 5 is a RAID level that uses disk striping with parity. It requires a minimum of three disks and can handle one disk failure. RAID 5 distributes the parity information across all the disks in the array, which improves the read performance and reduces the write penalty. The capacity of a RAID 5 array is (N-1) times the size of the smallest disk, where N is the number of disks in the array. Therefore, for six 4TB disks, the capacity of a RAID 5 array would be (6-1) x 4TB = 20TB, which meets the minimum disk space requirement of 19TB. RAID 5 also has the least amount of disk space lost to RAID overhead among the options, as it only uses one disk's worth of space for parity