What is the recommended RAID level when creating a Hitachi Dynamic Provisioning (HDP) pool?

Question

Options

• ARAID 1
• BRAID 1+0
• CRAID 5
• DRAID 6

• A
  4% (1)
• B
  8% (2)
• C
  4% (1)
• D
  85% (22)

Explanation

RAID 6 is the recommended level for HDP pools because it uses dual parity, tolerating two simultaneous drive failures - critical for large pools spanning many spindles where the statistical risk of a second failure during a rebuild is significant.

Why the distractors are wrong:

• RAID 1 (A): Pure mirroring is inefficient at scale (50% usable capacity) and not designed for the wide-stripe, high-capacity architecture HDP pools use.
• RAID 1+0 (B): Offers good performance but still only 50% capacity efficiency and higher cost per usable GB - impractical for thin-provisioned pools meant to maximize storage density.
• RAID 5 (C): Single parity can only survive one drive failure. As HDP pools grow to dozens of drives, the probability of a second failure during the lengthy rebuild window becomes unacceptably high.

Memory tip: Think "HDP = High Dual Protection" - the "D" in HDP reminds you of Dual parity, which maps directly to RAID 6's two independent parity blocks.

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