- A
Increase vm.dirty_ratio from 20 to 40.
Why wrong: Dirty_ratio sets the maximum percentage of dirty memory before processes are forced to write; increasing it could cause large, bursty writes, potentially increasing iowait.
- B
Increase vm.dirty_writeback_centisecs from 500 to 1000.
Increasing the interval between writeback cycles allows more dirty pages to accumulate, possibly merging writes and reducing the number of I/O operations, thus lowering iowait.
- C
Set vm.swappiness to 0.
Why wrong: Swappiness controls swap usage; setting to 0 avoids swapping unless necessary, but the high swap usage indicates memory pressure; this change might not reduce iowait and could even increase it if processes are swapped out less.
- D
Decrease vm.dirty_background_ratio from 10 to 5.
Why wrong: Dirty_background_ratio starts writeback earlier; decreasing it would write more frequently, likely increasing iowait.
Quick Answer
The answer is to increase vm.dirty_writeback_centisecs from 500 to 1000. This kernel parameter controls the interval between periodic writeback flushes, so raising it allows dirty pages to accumulate longer in memory before being written to disk, which reduces the frequency of write operations and can merge smaller writes into larger, more efficient I/O bursts—directly lowering I/O wait when the storage subsystem handles larger sequential writes well. On the CompTIA Linux+ XK0-005 exam, this question tests your understanding of how kernel parameters manage memory-to-disk write behavior under synchronous database workloads, and a common trap is confusing “dirty_ratio” (which controls how much dirty memory is allowed) with “dirty_writeback_centisecs” (which controls the timing of flushes). Remember: to reduce I/O wait, you want to slow down the writeback clock, not speed it up—think “writeback wait, not writeback weight.”
XK0-005 System Management Practice Question
This XK0-005 practice question tests your understanding of system management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 server is experiencing high I/O wait, as shown by the 'iostat -x' command: 'avg-cpu: %iowait=45' and '/dev/sda: await=120ms, %util=95%'. The server has 16 GB of RAM, and the administrator notices that the system is using a significant amount of swap: 'free -m' shows 4 GB of swap used out of 8 GB. The server runs a database application that performs many synchronous writes. The administrator wants to reduce I/O wait without adding physical memory. Which of the following kernel parameter changes is most likely to help by reducing the frequency of write operations to disk?
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 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
Increase vm.dirty_writeback_centisecs from 500 to 1000.
Increasing vm.dirty_writeback_centisecs (time between writeback flushes) allows more dirty pages to accumulate before being written, reducing write frequency and potentially merging writes, which can lower I/O wait if the I/O subsystem is efficient at handling larger writes. However, if the writeback interval is too high, it may increase burstiness. The other options: increasing dirty_ratio or dirty_background_ratio would allow more dirty pages in memory, which could temporarily reduce writes but might cause burstier writes and not reduce overall I/O wait. Decreasing dirty_writeback_centisecs would increase write frequency, likely worsening iowait. So Option C is the most plausible correct answer. Option D (swappiness) affects swap tendency, but swap usage indicates memory pressure; reducing swappiness might reduce swap but not directly address synchronous database writes.
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.
- ✗
Increase vm.dirty_ratio from 20 to 40.
Why it's wrong here
Dirty_ratio sets the maximum percentage of dirty memory before processes are forced to write; increasing it could cause large, bursty writes, potentially increasing iowait.
- ✓
Increase vm.dirty_writeback_centisecs from 500 to 1000.
Why this is correct
Increasing the interval between writeback cycles allows more dirty pages to accumulate, possibly merging writes and reducing the number of I/O operations, thus lowering iowait.
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.
- ✗
Set vm.swappiness to 0.
Why it's wrong here
Swappiness controls swap usage; setting to 0 avoids swapping unless necessary, but the high swap usage indicates memory pressure; this change might not reduce iowait and could even increase it if processes are swapped out less.
- ✗
Decrease vm.dirty_background_ratio from 10 to 5.
Why it's wrong here
Dirty_background_ratio starts writeback earlier; decreasing it would write more frequently, likely increasing iowait.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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.
What to study next
Got this wrong? Here's your next step.
Identify which XK0-005 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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System Management — study guide chapter
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System Management practice questions
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CompTIA Linux+ XK0-005 study guide
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FAQ
Questions learners often ask
What does this XK0-005 question test?
System Management — This question tests System Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase vm.dirty_writeback_centisecs from 500 to 1000. — Increasing vm.dirty_writeback_centisecs (time between writeback flushes) allows more dirty pages to accumulate before being written, reducing write frequency and potentially merging writes, which can lower I/O wait if the I/O subsystem is efficient at handling larger writes. However, if the writeback interval is too high, it may increase burstiness. The other options: increasing dirty_ratio or dirty_background_ratio would allow more dirty pages in memory, which could temporarily reduce writes but might cause burstier writes and not reduce overall I/O wait. Decreasing dirty_writeback_centisecs would increase write frequency, likely worsening iowait. So Option C is the most plausible correct answer. Option D (swappiness) affects swap tendency, but swap usage indicates memory pressure; reducing swappiness might reduce swap but not directly address synchronous database writes.
What should I do if I get this XK0-005 question wrong?
Identify which XK0-005 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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Last reviewed: Jun 24, 2026
This XK0-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the XK0-005 exam.
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