DBS-C01 Monitoring and Troubleshooting Practice Question

Correct answer & explanation

High CPU and high disk space usage on dc2.large nodes are classic signs of queries spilling to disk due to insufficient memory. When there isn't enough memory for query processing, Redshift resorts to writing intermediate results to disk, which increases disk space usage and also causes high CPU as the system manages the spill. Option A is insufficient network bandwidth: network bandwidth issues would typically manifest as increased network throughput or latency metrics, not high CPU and disk usage. Option B is CPU bottleneck: while CPU is high, the simultaneous high disk usage suggests the root cause is memory spilling, not CPU exhaustion alone. Adding compute nodes would not address the memory spilling if the workload is memory-intensive; instead, increasing the node size or using a different instance type with more memory per node would help. Option C is WLM queue: WLM queue waits would be visible in CloudWatch metrics like 'WLMQueueLength' or 'QueryWaitTime', not in CPU or disk usage.