Which RAID level provides data redundancy by mirroring?

• A. RAID 1 mirrors data for fault tolerance.
• B. RAID 0 stripes data for performance with no redundancy.
• C. RAID 5 uses parity for redundancy with a write penalty.
• D. RAID 10 combines mirroring and striping for both performance and redundancy.

Answer: (A)

Mirroring means keeping an exact copy of all data on a second disk, so if one drive fails you can continue without losing data. That is exactly what RAID 1 does: it writes identical data to two drives, providing fault tolerance and quick recovery. The other setups either have no redundancy (striping without parity), use parity to reconstruct data, or combine mirroring with striping (which is RAID 10), but the redundancy achieved specifically through mirroring points to RAID 1.