XK0-006 Troubleshooting Practice Question
A system is experiencing high disk I/O wait. Which command can provide disk I/O statistics such as requests per second and average wait time?
⚠ Common exam trap
XK0-006 often tests the difference between CPU-focused tools (sar -u, vmstat) and disk-focused tools (iostat -x) — candidates see 'iowait' in sar or vmstat output and assume those tools provide disk-level detail, which they do not.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
iostat -x 1
The iostat -x 1 command provides extended disk I/O statistics, including requests per second (r/s, w/s), average wait time (await), and utilization (%util), refreshed every second. This directly answers the need for per-device I/O performance data during high I/O wait.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
sar -u 1 5
Why it's wrong here
sar -u reports CPU utilisation statistics, not disk I/O, so it cannot supply requests per second or average wait time. It is tempting because sar with an interval samples activity over time, which suits CPU trend analysis, but the -u flag selects the CPU activity class rather than the -d disk class.
- ✓
iostat -x 1
Why this is correct
The -x flag extends iostat output with per-device metrics including requests per second, average queue size and average wait time, while the 1 sets a one-second sampling interval. This directly satisfies the requirement for disk I/O statistics during high wait.
- ✗
free -h
Why it's wrong here
free -h reports physical and swap memory usage in human-readable units, exposing no disk I/O counters at all. It is tempting because memory pressure can cause paging that inflates I/O wait, so it suits ruling out a RAM shortfall, but it cannot show requests per second or per-device wait time.
- ✗
vmstat 1 5
Why it's wrong here
vmstat 1 5 reports CPU, memory, paging and run-queue statistics; its bi/bo columns show block counts, not per-device requests per second or average wait time. It is tempting because it is a general performance sampler, which suits spotting overall system bottlenecks, but iostat provides the disk-level detail required.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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