سوال ۱۰۱ کنکور ارشد مهندسی کامپیوتر ۱۴۰۰

RAID (Redundant Array of Independent Disks) defines several organizations that trade off cost, performance and reliability. The question asks which level is disk mirroring.

• RAID 0 — striping only. Data is split across disks for performance, with no redundancy. A single disk failure loses data.
• RAID 1 — mirroring. Every block is written identically to a second (mirror) disk, so the array keeps a full duplicate copy. This is exactly disk mirroring; it survives the failure of one disk in a mirrored pair.
• RAID 2 — bit-level striping with Hamming-code (ECC) parity disks; rarely used.
• RAID 3 — byte-level striping with a single dedicated parity disk.

Since disk mirroring is the defining feature of RAID 1, the matching option is value $1$, which is choice 2 on the answer sheet.

Exam trick: Read the option carefully — the value is RAID level 1, but it is listed as the second option (option 1 holds the value 0). Mirroring = RAID 1; striping-only (no redundancy) = RAID 0; dedicated parity disk = RAID 4; distributed (block-interleaved) parity = RAID 5.