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Building and operationalizing data processing systems →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is to increase the project’s regional persistent disk quota, as the intermittent failures occur because every time a preemptible worker is reclaimed and replaced, the cluster attaches a new disk without immediately deleting the old one, causing a buildup of unattached disks that exhausts the quota. This technical behavior stems from the fact that Dataproc does not automatically clean up orphaned disks from preempted instances, so the quota is consumed by temporary disks that linger in the region. On the Google Professional Data Engineer exam, this scenario tests your understanding of how preemptible workers interact with resource quotas, often appearing as a trap where candidates mistakenly blame the disk size or node count rather than the regional quota limit. A common memory tip is to think of preemptible workers as “disk hoarders”—they leave behind old disks when they restart, so you must pre-allocate extra quota to accommodate the buildup.

PDE Practice Question: Building and operationalizing data processing systems

This PDE practice question tests your understanding of building and operationalizing data processing systems. 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 company runs a Dataproc cluster for nightly batch jobs. The cluster uses preemptible workers for cost savings. Recently, the jobs have been failing intermittently with 'Disk quota exceeded' errors on the persistent disks attached to the preemptible workers. The cluster is configured with a master node and 10 worker nodes, each with a 100 GB persistent disk. The preemptible workers are dynamically added and removed. What is the most likely cause and the best long-term solution?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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.

Question 1hardmultiple choice

Full question →

A
The persistent disks of the preemptible workers are too small. Resize the persistent disks to 200 GB each.
Why wrong: D is wrong because the error is about quota, not size; resizing disks would not resolve quota exhaustion.
B
The preemptible workers are using local SSDs that are not recreated on reclaim. Use non-preemptible workers with local SSDs instead.
Why wrong: C is wrong because the error mentions persistent disks, not SSDs, and local SSDs are not default for Dataproc preemptible workers.
C
The preemptible workers are exceeding the project's persistent disk quota in the region because every time a preempted worker restarts, it tries to attach a new disk. Increase the disk quota.
A is correct because preemptible workers can cause disk quota exhaustion due to rapid creation/deletion of persistent disks.
D
The preemptible workers do not have enough persistent disk space to store intermediate shuffle data. Switch to standard workers to avoid this issue.
Why wrong: B is wrong because the error is 'Disk quota exceeded' not 'disk full', and switching to standard workers removes the cost advantage.

Full breakdown with real-world context →

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

✓

The preemptible workers are exceeding the project's persistent disk quota in the region because every time a preempted worker restarts, it tries to attach a new disk. Increase the disk quota.

Option C is correct because the intermittent 'Disk quota exceeded' errors on preemptible workers are caused by the project's regional persistent disk quota being exhausted. When a preemptible worker is reclaimed, the cluster attempts to attach a new persistent disk to the replacement worker, but the old disk is not immediately deleted, leading to a buildup of unattached disks that consume quota. The best long-term solution is to increase the persistent disk quota in the region to accommodate the temporary disks from preempted workers.

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 persistent disks of the preemptible workers are too small. Resize the persistent disks to 200 GB each.
Why it's wrong here
D is wrong because the error is about quota, not size; resizing disks would not resolve quota exhaustion.
✗
The preemptible workers are using local SSDs that are not recreated on reclaim. Use non-preemptible workers with local SSDs instead.
Why it's wrong here
C is wrong because the error mentions persistent disks, not SSDs, and local SSDs are not default for Dataproc preemptible workers.
✓
The preemptible workers are exceeding the project's persistent disk quota in the region because every time a preempted worker restarts, it tries to attach a new disk. Increase the disk quota.
Why this is correct
A is correct because preemptible workers can cause disk quota exhaustion due to rapid creation/deletion of persistent disks.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The preemptible workers do not have enough persistent disk space to store intermediate shuffle data. Switch to standard workers to avoid this issue.
Why it's wrong here
B is wrong because the error is 'Disk quota exceeded' not 'disk full', and switching to standard workers removes the cost advantage.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates mistakenly attribute the error to insufficient disk size or shuffle data capacity, rather than recognizing it as a regional quota exhaustion issue caused by orphaned disks from preempted workers.

Detailed technical explanation

How to think about this question

In Google Cloud Dataproc, preemptible workers use standard persistent disks by default, and when a worker is preempted, the disk is not automatically deleted; it remains as an unattached disk in the project, consuming quota. The cluster's autoscaler or node manager creates a new disk for the replacement worker, leading to a rapid accumulation of unattached disks that can exceed the regional persistent disk quota (default 10 TB per region). This is a common pitfall in environments with high preemption rates, and the solution is to request a quota increase or implement a cleanup mechanism for orphaned 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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this PDE question test?

Building and operationalizing data processing systems — This question tests Building and operationalizing data processing systems — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The preemptible workers are exceeding the project's persistent disk quota in the region because every time a preempted worker restarts, it tries to attach a new disk. Increase the disk quota. — Option C is correct because the intermittent 'Disk quota exceeded' errors on preemptible workers are caused by the project's regional persistent disk quota being exhausted. When a preemptible worker is reclaimed, the cluster attempts to attach a new persistent disk to the replacement worker, but the old disk is not immediately deleted, leading to a buildup of unattached disks that consume quota. The best long-term solution is to increase the persistent disk quota in the region to accommodate the temporary disks from preempted workers.

What should I do if I get this PDE 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: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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