XK0-006 Troubleshooting Practice Question
An administrator wants to monitor disk I/O performance in real-time, focusing on metrics like wait time and I/O queue size. Which tool is best suited for this?
⚠ Common exam trap
XK0-006 often tests the distinction between real-time per-device tools (iostat -x) and aggregate or historical tools (vmstat, sar), so candidates who pick vmstat for 'wait time and queue size' fall into the trap of confusing summary I/O counters with extended device metrics.
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
iostat -x 1 provides extended disk statistics refreshed every second, including await (average wait time), svctm, %util, and avgqu-sz (average queue size), which directly match the requested metrics. The -x flag enables the extended report that exposes per-device wait and queue depth, making it the correct real-time tool.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
vmstat
Why it's wrong here
vmstat reports CPU, memory, paging and block I/O counts, but not per-device wait time or queue size. It is tempting because it does show some I/O columns, and would be the right choice for a quick overall system snapshot of runnable processes and swap activity.
- ✗
sar -b
Why it's wrong here
sar -b reports historical I/O transfer rates from archived data, not real-time per-device wait time or queue depth. It is tempting because it does cover disk activity, and would be the correct choice when reviewing past I/O trends rather than monitoring live.
- ✗
free -h
Why it's wrong here
free -h displays memory and swap usage only, with no disk I/O metrics whatsoever. It is tempting because memory pressure can indirectly cause I/O, and would be the right tool when checking available RAM and swap consumption.
- ✓
iostat -x 1
Why this is correct
The -x flag extends iostat output to include per-device metrics such as average wait time (await) and queue size (aqu-sz), while the interval argument 1 refreshes these statistics every second, satisfying the real-time monitoring requirement in the stem.
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JA
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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