ITPEC FE Morning April 2019 Question 13
Which of the following is an appropriate description concerning the recording method of RAID5?
Explanation
Block-level striping with distributed parity — RAID 5 stripes data in blocks and rotates the parity block across all the disks.
For each stripe, one disk holds the parity of the other disks' blocks, and which disk that is changes from stripe to stripe. Any single disk can fail and its contents are rebuilt from the others. Spreading the parity avoids one parity disk that every write must update.
The levels the options describe:
- •RAID 1: mirroring, the same data on two disks
- •RAID 2: bit-level striping with Hamming (ECC) code disks
- •RAID 3: byte-level striping, one dedicated parity disk
- •RAID 5: block-level striping, parity distributed over all disks
Answer (b)
Why not others:
- •(a) — bit-level striping with ECC written on several disks is RAID 2
- •(c) — byte-level striping with parity on one dedicated disk is RAID 3
- •(d) — writing the same data on two disks is mirroring, RAID 1
Key rule: RAID 3, 4 and 5 all spend one disk's worth of space on parity; they differ in the striping unit (byte or block) and in whether the parity sits on one disk or rotates.
System Component · AI-written, may contain errors
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