D-UN-OE-23 · Question #24
A system administrator wants to limit I/O for the following LUNs: - LUN A: Size 100 GB, Limit:500 IOPS - LUN B: Size 500 GB, Limit: 1000 1OPS - LUN C: Size 500 GB, Limit: 500 1OPS - LUN D: Size 1000…
The correct answer is B. Two absolute limit policies. Option B is correct because the four LUNs can be grouped by their absolute IOPS limits into exactly two groups: a 500 IOPS policy covering LUN A and LUN C, and a 1000 IOPS policy covering LUN B and LUN D. An absolute limit policy caps I/O at a fixed value regardless of LUN…
Question
A system administrator wants to limit I/O for the following LUNs:
- LUN A: Size 100 GB, Limit:500 IOPS
- LUN B: Size 500 GB, Limit: 1000 1OPS
- LUN C: Size 500 GB, Limit: 500 1OPS
- LUN D: Size 1000 GB, Limit: 1000 1OPS
What type and number of host I/O limit policies must be used?
Options
- AOne shared absolute limit policy
- BTwo absolute limit policies
- COne absolute policy and one density based limit policy
- DTwo density based limit policies
How the community answered
(31 responses)- A6% (2)
- B55% (17)
- C10% (3)
- D29% (9)
Explanation
Option B is correct because the four LUNs can be grouped by their absolute IOPS limits into exactly two groups: a 500 IOPS policy covering LUN A and LUN C, and a 1000 IOPS policy covering LUN B and LUN D. An absolute limit policy caps I/O at a fixed value regardless of LUN size, making this the simplest and most efficient solution here.
Why the distractors fail:
- A (One shared absolute policy) is wrong because the LUNs have two distinct IOPS ceilings (500 and 1000), so no single absolute limit policy can satisfy all four requirements simultaneously.
- C (One absolute + one density-based) is unnecessary complexity - mixing policy types is only warranted when the limits scale with LUN size, which isn't required here.
- D (Two density-based policies) fails because density-based limits are expressed as IOPS-per-GB. Computing the densities (LUN A = 5 IOPS/GB, B = 2 IOPS/GB, C = 1 IOPS/GB, D = 1 IOPS/GB) reveals three distinct densities, so you'd need at least three policies - not two.
Memory tip: Ask yourself "do the limits scale with size?" If yes → density-based. If no → absolute. Then count how many unique limit values exist - that tells you the minimum number of policies needed. Here, two unique absolute values (500 and 1000 IOPS) → two absolute policies.
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