Which RAID level would you select if reliability is the priority and you want good random write performance?

• A. RAID 10
• B. RAID 1
• C. RAID 0
• D. RAID 5

Answer: (A)

Reliability with fast random writes is achieved by combining mirroring with striping. In RAID 10, data is mirrored on pairs of drives and then those mirrors are striped across multiple pairs. This provides redundancy because each piece of data exists on two drives, so a single drive failure in any pair doesn’t lose the data. If a drive fails, the system keeps operating with the remaining drives, and the data remains available from its mirror.

For random write performance, RAID 10 is efficient because writes go to both disks in a mirrored pair, avoiding the parity calculations used by RAID 5. Since the data is striped across several mirrors, multiple write operations can be handled in parallel across different pairs, delivering higher throughput than a simple mirrored set. In contrast, RAID 0 has no redundancy, RAID 1 offers redundancy but limited write throughput, and RAID 5 incurs parity overhead that slows random writes.