CV0-004 Troubleshooting Practice Question
A cloud engineer is troubleshooting a storage performance issue. The storage is backed by a SAN with a mix of SSD and HDD drives. Which of the following metrics would BEST indicate that the storage subsystem is the bottleneck?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
High disk queue depth and latency
High disk queue depth and latency directly indicate that I/O requests are waiting, which is a classic sign of a storage bottleneck. Low memory usage (A) does not indicate a storage issue. High network utilization (B) could be caused by storage traffic but does not confirm the storage subsystem is the bottleneck; it could be normal. High CPU utilization (D) points to compute, not storage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Low memory usage on the hypervisor
Why it's wrong here
Low hypervisor memory usage says nothing about disk throughput or latency; a SAN bottleneck shows as high disk queue depth or elevated read/write latency. Memory metrics are tempting because they are easy to collect, but they belong to a capacity-planning scenario for RAM, not storage contention.
- ✗
High network utilization on storage network links
Why it's wrong here
Storage network utilisation measures the fabric carrying I/O, so saturation there indicates a network bottleneck rather than the SAN's disk tier. High link utilisation is the correct signal when the interconnect is the constraint, but the stem asks about the storage subsystem's own drives.
- ✓
High disk queue depth and latency
Why this is correct
Queue depth measures outstanding I/O requests awaiting service, and latency measures response time. Both rising together shows requests are queuing faster than the SSD/HDD mix can serve them, isolating the storage subsystem rather than CPU, network or application as the bottleneck.
- ✗
High CPU utilization on all application servers
Why it's wrong here
Application server CPU utilisation reflects compute demand, not storage latency; a saturated SAN can leave CPUs idle waiting on I/O. CPU is the right metric when the bottleneck is processing, whereas the stem asks which measurement isolates the storage subsystem itself.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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