Diagnose Storage I/O Performance and Identify the Workload

A service is slow and storage I/O is suspected. Explain how you would use system metrics such as iostat, identify the responsible workload, and decide whether the storage path is the bottleneck. ### Constraints & Assumptions No device type or filesystem is specified. Interpret queueing, latency, and utilization in the context of the actual storage stack rather than assuming one threshold applies to every disk or SSD. ### Clarifying Questions Are reads or writes slow? Is the pattern random or sequential? What are the request size, concurrency, caching, and durability requirements? Does the application wait on sync or metadata operations? ### What a Strong Answer Covers Device-level latency and throughput, process attribution, cache effects, workload shape, and a measured remediation plan. ### Follow-up Questions Why is a high utilization percentage not sufficient to prove saturation on every device? How would you separate application queueing from device service time? What changes when storage is remote?