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Systems & Data Center · Advanced

Queue Depth

The number of outstanding I/O requests that can be pending to a storage device or path at one time.

Definition

Higher queue depth enables more parallelism, but if the device cannot keep up, queuing adds latency. HBAs, LUNs and hypervisors each have queue depth limits that may need tuning.

Example

Increasing the HBA LUN queue depth from 32 to 64 relieves latency on a busy datastore.

Exam tip

Queue depth mismatches between host and array can cause queuing latency.

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