Which RAID level protects against two concurrent data drive failures?

RAID 2 uses bit-level striping with Hamming error-correcting code and is an obsolete, theoretical level that provides no practical two-drive failure protection in modern implementations.

RAID 3 uses byte-level striping with a single dedicated parity drive and can only tolerate the loss of one drive before the array fails.

RAID 5 uses block-level striping with single distributed parity and can only survive a single drive failure - a second concurrent failure results in permanent data loss.

RAID 6 writes two separate parity blocks distributed across all member drives, so any two drives can fail simultaneously and the array remains operational and data-consistent. This dual-parity design directly addresses the requirement of protecting against two concurrent drive failures, which single-parity RAID levels cannot achieve.