This XK0-005 practice question tests your understanding of troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A Linux administrator is troubleshooting a server that is running slowly. The 'sar -q' command shows a run queue length of 12 and a load average of 8.5. The CPU utilization is 90% idle. Which of the following is the most likely cause of the performance issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The disk I/O subsystem is a bottleneck, causing processes to wait for I/O.
The 'sar -q' output shows a high run queue length (12) and load average (8.5) despite 90% CPU idle. This indicates that processes are in an uninterruptible sleep state (D state) waiting for I/O, not contending for CPU. A disk I/O bottleneck causes processes to queue for I/O completion, inflating the load average while CPU remains idle, making D the correct answer.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The CPU is overloaded and needs to be upgraded.
Why it's wrong here
CPU is 90% idle, so it is not overloaded.
✗
The network interface is saturated.
Why it's wrong here
Network saturation would not cause high run queue with idle CPU.
✗
The system is low on memory and swapping heavily.
Why it's wrong here
Memory pressure would show high swap usage and possibly high I/O wait, but the primary indicator is high run queue with idle CPU.
✓
The disk I/O subsystem is a bottleneck, causing processes to wait for I/O.
Why this is correct
High run queue with idle CPU typically means I/O wait; processes are in 'D' state waiting for disk.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see a high load average and assume CPU overload, but the 90% idle CPU reveals the load is from I/O-waiting processes, not CPU contention.
Trap categories for this question
Command / output trap
Memory pressure would show high swap usage and possibly high I/O wait, but the primary indicator is high run queue with idle CPU.
Detailed technical explanation
How to think about this question
The load average in Linux counts processes in a runnable or uninterruptible sleep state (TASK_UNINTERRUPTIBLE). When disk I/O is slow, processes waiting for I/O remain in D state, contributing to the load average without consuming CPU cycles. The 'sar -q' command reports the run queue length as the number of tasks waiting for CPU plus those in D state; a high value with low CPU usage strongly points to I/O wait. Tools like 'iostat -x' or 'pidstat -d' can confirm high await times or high %util on specific disks.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the XK0-005 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The disk I/O subsystem is a bottleneck, causing processes to wait for I/O. — The 'sar -q' output shows a high run queue length (12) and load average (8.5) despite 90% CPU idle. This indicates that processes are in an uninterruptible sleep state (D state) waiting for I/O, not contending for CPU. A disk I/O bottleneck causes processes to queue for I/O completion, inflating the load average while CPU remains idle, making D the correct answer.
What should I do if I get this XK0-005 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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