An ops team wants CloudWatch alarms on EC2 memory utilization and disk space. CPUUtilization works fine, but memory and disk metrics don't appear in CloudWatch. Why, and what's the fix?
A.Enable detailed monitoring — memory is a detailed-only metric
Detailed monitoring changes the metric interval (1 min vs 5 min), not the metric set.
B.Install and configure the CloudWatch agent to publish OS-level metrics
Correct. OS-level metrics come only from the in-guest agent.
C.Memory metrics require CloudWatch Insights subscription
Logs Insights queries logs — it doesn't unlock memory metrics.
D.Move the instance to a larger type; small instances don't report memory
Instance type doesn't gate which OS metrics exist — the agent does.
Why this answer
CloudWatch collects hypervisor-level metrics automatically (CPU, network, disk I/O, status checks) — but OS-level metrics like memory utilization and disk usage require the CloudWatch agent installed inside the instance.
Correct answer: B · Last reviewed 2026-10-26
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