The answer is that the boot disk is too small and has run out of space, causing the instance to become unresponsive. When a Compute Engine boot disk reaches 95% capacity on a 100 GB disk, only 5 GB remains, which is easily exhausted by the operating system’s need to write temporary files, logs, and perform essential system operations—processes like systemd or journald on Linux, or the Windows Registry, can freeze when they cannot write to the root device. On the Google Professional Cloud Architect exam, this scenario tests your understanding of disk sizing and OS dependencies, often appearing as a trap where candidates focus on the large data disk instead of the critical boot disk. A common memory tip is to remember that the boot disk is the OS’s lifeline: if it’s full, the instance goes silent, regardless of how much space is on attached data disks. Think of it as “boot disk first, data disk later” to avoid missing the root cause.
Google PCA Manage implementation of cloud architecture Practice Question
This PCA practice question tests your understanding of manage implementation of cloud architecture. 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.
Network Topology
An engineer runs the command above. A few days later, the instance becomes unresponsive. Upon investigation, you find that the boot disk is 100 GB and 95% full. The data disk is 500 GB and only 20% full. What is the most likely cause of the unresponsiveness?
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 boot disk is too small and has run out of space.
The boot disk is 95% full, which leaves insufficient free space for the operating system to write temporary files, logs, or perform essential system operations. When a Linux or Windows boot disk runs out of space, the OS can become unresponsive because critical processes (e.g., systemd, journald, or the Windows Registry) cannot write to disk. In Google Cloud, the boot disk is the root device (typically /dev/sda1), and filling it to 95% on a 100 GB disk means only 5 GB remains, which is easily exhausted by normal system activity.
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 boot disk is too small and has run out of space.
Why this is correct
95% full boot disk can cause system instability and unresponsiveness.
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.
✗
The data disk is pd-standard, which is causing I/O bottlenecks for the OS.
Why it's wrong here
The OS is on the boot disk, not the data disk.
✗
The boot disk is pd-ssd, which is too slow for the workload.
Why it's wrong here
pd-ssd is fast; performance is not the issue.
✗
The instance has run out of IOPS on the boot disk.
Why it's wrong here
pd-ssd has high IOPS; not likely exhausted.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between disk space exhaustion and performance bottlenecks; the trap here is that candidates may focus on disk type (pd-standard vs pd-ssd) or IOPS limits instead of recognizing that a nearly full boot disk directly causes OS unresponsiveness.
Detailed technical explanation
How to think about this question
Under the hood, when the boot disk reaches 95% capacity, the OS may still have a small amount of reserved space for root (typically 5% on ext4 filesystems), but once that is consumed, write operations fail with 'No space left on device' errors. This can prevent critical system services like sshd or cron from writing logs or PID files, leading to a hung instance. In Google Cloud, the boot disk is mounted at / and includes /var, /tmp, and /home by default, so filling it affects all system directories.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Manage implementation of cloud architecture — This question tests Manage implementation of cloud architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The boot disk is too small and has run out of space. — The boot disk is 95% full, which leaves insufficient free space for the operating system to write temporary files, logs, or perform essential system operations. When a Linux or Windows boot disk runs out of space, the OS can become unresponsive because critical processes (e.g., systemd, journald, or the Windows Registry) cannot write to disk. In Google Cloud, the boot disk is the root device (typically /dev/sda1), and filling it to 95% on a 100 GB disk means only 5 GB remains, which is easily exhausted by normal system activity.
What should I do if I get this PCA 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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