- A
Locally redundant storage (LRS)
Why wrong: LRS replicates data three times within a single physical datacenter. If that entire datacenter fails, the data becomes unavailable or could be lost. This does not meet the requirement to survive a datacenter failure.
- B
Zone-redundant storage (ZRS)
ZRS replicates data across three Azure availability zones in the primary region. Each zone is an independent datacenter. This ensures data availability if one datacenter fails, and it is less expensive than geo-redundant storage because it does not use a secondary region.
- C
Geo-redundant storage (GRS)
Why wrong: GRS replicates data to a secondary region that is hundreds of miles away, providing protection against a full regional outage. However, it is significantly more expensive than ZRS and the company only needs protection against a single datacenter failure, making ZRS a more cost-effective choice.
- D
Read-access geo-redundant storage (RA-GRS)
Why wrong: RA-GRS provides the same geo-redundancy as GRS but also enables read access to the secondary region. It offers more durability than ZRS but at a higher cost. For the requirement of protecting against a single datacenter failure with minimal cost, ZRS is the optimal option.
Quick Answer
The correct choice is Zone-redundant storage (ZRS) because it synchronously replicates your data across three separate Azure availability zones within a single region, ensuring continuous availability even if an entire datacenter fails due to a fire or power outage. This meets the requirement for Azure storage redundancy for datacenter failure protection at low cost, as ZRS avoids the expensive cross-region bandwidth charges incurred by geo-redundant options like GRS. On the AZ-900 exam, this question tests your ability to match redundancy tiers to specific business scenarios—common traps include confusing ZRS with locally redundant storage (LRS), which only protects against drive failures within one datacenter, not a full datacenter outage. Remember the memory tip: “ZRS = Zero Region Switch” — it keeps data safe across zones without leaving the region, saving you money.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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 stores critical business data in an Azure Storage account. The data must remain available if a single Azure datacenter experiences a failure (e.g., fire, power outage). The company wants to minimize storage costs. Which storage redundancy option should they choose?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Zone-redundant storage (ZRS)
Zone-redundant storage (ZRS) synchronously replicates data across three Azure availability zones within a single region, ensuring data remains available if an entire datacenter fails. This meets the requirement for datacenter failure protection while minimizing costs compared to geo-redundant options, as ZRS does not incur cross-region bandwidth charges.
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.
- ✗
Locally redundant storage (LRS)
Why it's wrong here
LRS replicates data three times within a single physical datacenter. If that entire datacenter fails, the data becomes unavailable or could be lost. This does not meet the requirement to survive a datacenter failure.
- ✓
Zone-redundant storage (ZRS)
Why this is correct
ZRS replicates data across three Azure availability zones in the primary region. Each zone is an independent datacenter. This ensures data availability if one datacenter fails, and it is less expensive than geo-redundant storage because it does not use a secondary region.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Geo-redundant storage (GRS)
Why it's wrong here
GRS replicates data to a secondary region that is hundreds of miles away, providing protection against a full regional outage. However, it is significantly more expensive than ZRS and the company only needs protection against a single datacenter failure, making ZRS a more cost-effective choice.
- ✗
Read-access geo-redundant storage (RA-GRS)
Why it's wrong here
RA-GRS provides the same geo-redundancy as GRS but also enables read access to the secondary region. It offers more durability than ZRS but at a higher cost. For the requirement of protecting against a single datacenter failure with minimal cost, ZRS is the optimal option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose LRS because it is the cheapest option, forgetting that LRS does not protect against a full datacenter failure, which is explicitly required in the scenario.
Detailed technical explanation
How to think about this question
ZRS uses synchronous replication across three availability zones, each with independent power, cooling, and networking, providing a Recovery Point Objective (RPO) of zero and a Recovery Time Objective (RTO) of minutes for most operations. Under the hood, Azure Storage uses a distributed consensus protocol to ensure consistency across zones, and the data is stored in three separate copies, each in a different fault domain. In a real-world scenario, if a zone experiences a fire, ZRS automatically fails over to another zone without manual intervention, maintaining read and write access.
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 AZ-900 question test?
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Zone-redundant storage (ZRS) — Zone-redundant storage (ZRS) synchronously replicates data across three Azure availability zones within a single region, ensuring data remains available if an entire datacenter fails. This meets the requirement for datacenter failure protection while minimizing costs compared to geo-redundant options, as ZRS does not incur cross-region bandwidth charges.
What should I do if I get this AZ-900 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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 2026
This AZ-900 practice question is part of Courseiva's free Microsoft 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 AZ-900 exam.
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