(A company is using the CloudWatch agent on its EC2 Linux instances.

The `disk_io_time` metric, collected by the CloudWatch agent on EC2 Linux instances, measures the total time (in milliseconds) that read and write requests have waited on I/O, helping to assess disk performance for instance sizing. The WGU Cloud Deployment and Operations Study Guide (Section 4.1, CloudWatch Agent Metrics) states, "The `disk_io_time` metric, available via the CloudWatch agent, tracks the time spent waiting for I/O operations, providing insight into disk contention for optimizing EC2 instance sizing." disk_read_ops, diskio_reads, and diskio_read_bytes measure operation counts or bytes, not wait times.