Which commands display disk I/O statistics and help identify top I/O wait processes (assuming iotop is installed)?

• A. iostat -xz 1 2; iotop (if installed)
• B. df -h; top
• C. lsblk; du -h
• D. pmap; sar

Answer: (A)

When diagnosing disk I/O bottlenecks, you want both system-wide I/O statistics and visibility into which processes are waiting on I/O. iostat with extended statistics shows per-device metrics like utilization, throughput, and the average wait time (await), giving a clear view of where I/O activity is happening. The flags -x enable the extended stats, -z suppresses devices with no activity, and running it with a short interval (1) and a small count (2) updates the display in real time so you can spot spikes.

If iotop is installed, it adds a per-process view of I/O usage and the I/O wait time for each process. This combination lets you directly identify which processes are contributing most to I/O wait and tie that to the device-level stats you see with iostat.

Other options don’t provide both perspectives: df shows disk usage, not I/O performance; top focuses on CPU and general process info rather than I/O wait per process; lsblk and du deal with device structure and directory sizes; pmap is about memory mappings; sar can collect I/O data but doesn’t by itself highlight the top I/O-wait processes the way iotop does.