ITPEC FE Morning April 2020 Question 14
A RAID 6 server is configured with six hard disk drives, and each drive’s capacity is one TB. What is the maximum total data storage capacity in TB? Here, spare disks are not used.
Explanation
4 TB — RAID 6 gives up two drives' worth of capacity to its two parity blocks per stripe.
RAID 6 stripes data across all drives and adds two independent parity blocks to every stripe, spread over the drives, so any two drives can fail without data loss. With N drives, the usable capacity is that of N − 2 drives: (6 − 2) × 1 = 4 TB.
Answer (b)
Why not others:
- •(a) 3 — half the drives, the capacity under mirroring (RAID 1 or RAID 10), not under parity
- •(c) 5 — N − 1 drives, the capacity of RAID 5 with a single parity block per stripe
- •(d) 6 — the full raw capacity, as in RAID 0 with no redundancy at all
Key rule: Each parity block per stripe costs one drive of capacity: RAID 5 loses one drive, RAID 6 two, and mirroring loses half.
System Component · AI-written, may contain errors
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