You are configuring external storage with Hitachi Device Manager on a VSP. What happens when you set the Cache Mode parameter to Enable?

Question

Options

• AAfter receiving the data into its cache memory, the VSP signals the host that an I/O operation has
• BAfter receiving the data into its cache memory, the VSP signals the host that an I/O operation has
• CThe VSP will always use its cache for every operation.
• DThe VSP will always use the cache in the remote storage system for every operation.

• A
  74% (42)
• B
  4% (2)
• C
  7% (4)
• D
  16% (9)

Explanation

Cache Mode = Enable activates write-back caching on the VSP: once data lands in the VSP's own cache, the VSP immediately signals the host that the write I/O is complete - without waiting for the data to be flushed to the external storage system. This improves write performance significantly because the host is freed to issue the next I/O right away.

Why the distractors are wrong:

• B is a trick - it appears identical to A but likely completes differently (e.g., "has not completed"), which inverts the behavior and describes a scenario where the VSP waits before acknowledging, negating the performance benefit.
• C is wrong because Cache Mode Enable is specifically about write behavior (acknowledging to the host after cache write), not a blanket "use cache for everything" policy.
• D is wrong because enabling Cache Mode uses the VSP's own cache, not the remote/external storage system's cache - the whole point is to avoid relying on the external device for response time.

Memory tip: Think of Cache Mode Enable as the VSP saying "I've got it, you're done" the moment data hits its cache - like a relay runner grabbing the baton and immediately letting the previous runner rest, rather than making them wait until the finish line.

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