PCA Promql Practice Question
An engineer needs to determine the total absolute increase in disk space consumed over the last 3 hours using a gauge metric node_disk_bytes_used. Which function is appropriate?
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
✓
delta(node_disk_bytes_used[3h])
The increase() function is designed for counters, but delta() calculates the difference between the first and last value of a range vector, making it suitable for gauges.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
deriv(node_disk_bytes_used[3h])
Why it's wrong here
deriv calculates the per-second derivative of the gauge using simple linear regression.
- ✗
increase(node_disk_bytes_used[3h])
Why it's wrong here
increase is intended for counters and automatically handles counter resets.
- ✗
rate(node_disk_bytes_used[3h])
Why it's wrong here
rate is strictly for counters and calculates a per-second average.
- ✓
delta(node_disk_bytes_used[3h])
Why this is correct
Correct. delta calculates the difference between start and end values of a range vector for gauges.
About these practice questions
This PCA question is part of Courseiva's 304-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CNCF / Linux Foundation exam blueprint
This PCA practice question is part of Courseiva's free CNCF / Linux Foundation 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 PCA exam.