ITPEC FE Morning October 2020 Question 15
Topic: System Component
Which of the following achieves data redundancy via mirroring?
Explanation
RAID 1 — mirroring writes the same data to two disks, so either disk alone holds a full copy.
- •RAID 0: striping only, data spread across disks for speed, no redundancy
- •RAID 1: mirroring, an identical copy on a second disk
- •RAID 5: striping with one parity block per stripe, distributed across disks; survives one disk failure
- •RAID 6: striping with two parity blocks per stripe; survives two disk failures
Answer (b)
Why not others:
- •(a) RAID 0 — stripes data with no redundancy at all; losing one disk loses the array
- •(c) RAID 5 — gets redundancy from parity, rebuilding lost data by calculation, not from a mirror copy
- •(d) RAID 6 — the same idea as RAID 5 with double parity, again not mirroring
Key rule: RAID redundancy comes either from copies (RAID 1, mirroring, 50% usable capacity) or from parity (RAID 5 and 6, one or two disks' worth of capacity lost).
System Component · AI-written, may contain errors
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