How many drives are required for RAID 50 to maintain fault tolerance against two drive failures?

RAID 50 is a nested RAID level that combines RAID 5 and RAID 0, providing both improved performance and fault tolerance. To understand how many drives are necessary to maintain fault tolerance against two drive failures in a RAID 50 configuration, it is important to know how RAID 5 works. RAID 5 requires a minimum of three drives, providing fault tolerance against a single drive failure.

In a RAID 50 setup, multiple RAID 5 arrays are striped together to form a single logical unit. Each of these RAID 5 arrays can tolerate one drive failure. If you want RAID 50 to sustain two drive failures, it means you should have at least two RAID 5 arrays, each being able to lose one drive while remaining operational. Therefore, to ensure reliable fault tolerance, the minimum number of drives needed for two RAID 5 arrays (each requiring at least three drives) would be six.

Thus, with two RAID 5 arrays, each consisting of three drives, you achieve both the required number of drives to support the necessary fault tolerance as well as a balanced configuration that maximizes both performance and redundancy. This is why the answer of six drives is correct.