What metric can be monitored using Amazon CloudWatch to gauge EC2 performance?

CPU utilization is a critical metric that can be monitored using Amazon CloudWatch to gauge the performance of Elastic Compute Cloud (EC2) instances. It reflects the percentage of the allocated EC2 instance's CPU capacity that is currently being utilized. By tracking this metric, users can assess whether their instances are appropriately sized for the workloads they are handling. High CPU utilization may indicate that the instance is under heavy load, which could necessitate scaling up the instance type or distributing the workload across multiple instances. Conversely, consistently low CPU utilization could suggest that an instance is over-provisioned, leading to unnecessary costs.

While Disk I/O and Network latency are also important metrics for gauging performance, they are not as central to the direct assessment of CPU performance as CPU utilization. Memory usage, although a vital aspect of overall server health, is not natively monitored by CloudWatch unless custom metrics are set up, making CPU utilization the more straightforward metric for immediate performance insight in standard EC2 settings.