Which RAID level uses double parity to provide fault tolerance against two simultaneous disk failures?

Which RAID level uses double parity to provide fault tolerance against two simultaneous disk failures?

• A. RAID 0
• B. RAID 5
• C. RAID 6
• D. RAID 1

Answer: (C)

Two-parity storage arrays provide fault tolerance for two disk failures by storing two independent parity blocks across the disks. Parity data lets you reconstruct original data if a disk fails. With a single parity scheme, you can recover from one failed disk, but a second failure would leave you with unrecoverable data. By adding a second, independent parity calculation, the array can rebuild data even if any two disks fail. The parity information is distributed across all disks, so losing any two disks still leaves enough information to restore the missing data. Because two disks are dedicated to parity, usable capacity is reduced by two disks’ worth of space, and this setup is commonly implemented with four or more disks to balance capacity, performance, and fault tolerance. The tradeoff is higher write overhead and more complex parity handling, but it delivers protection against two simultaneous disk failures.

Two-parity storage arrays provide fault tolerance for two disk failures by storing two independent parity blocks across the disks. Parity data lets you reconstruct original data if a disk fails. With a single parity scheme, you can recover from one failed disk, but a second failure would leave you with unrecoverable data. By adding a second, independent parity calculation, the array can rebuild data even if any two disks fail. The parity information is distributed across all disks, so losing any two disks still leaves enough information to restore the missing data. Because two disks are dedicated to parity, usable capacity is reduced by two disks’ worth of space, and this setup is commonly implemented with four or more disks to balance capacity, performance, and fault tolerance. The tradeoff is higher write overhead and more complex parity handling, but it delivers protection against two simultaneous disk failures.