- A
Locally Redundant Storage (LRS)
Why wrong: LRS replicates data three times within a single datacenter. This protects against hardware failures within the datacenter but does not protect against an entire datacenter outage. Therefore, it would not meet the requirement for availability if a datacenter fails.
- B
Zone-Redundant Storage (ZRS)
ZRS replicates data synchronously across three Azure availability zones in the same region. If one zone (datacenter) goes down, the data remains available from the other zones. This is the correct choice for ensuring that managed disks survive a full datacenter failure within a single region.
- C
Geo-Redundant Storage (GRS)
Why wrong: GRS replicates data to a secondary region for disaster recovery. However, GRS is not supported for Azure managed disks. It is designed for Azure storage accounts (blobs, files, queues, tables). Additionally, the requirement is only for within-region availability, not cross-region, so GRS would be overkill and unsupported.
- D
Read-Access Geo-Redundant Storage (RA-GRS)
Why wrong: RA-GRS is similar to GRS but also allows read access to the data in the secondary region. Like GRS, it is not available for managed disks and is intended for storage accounts. It also provides cross-region protection, which is not needed here.
Quick Answer
Zone-Redundant Storage (ZRS) is the correct choice because it synchronously replicates your managed disk data across three separate Azure availability zones within the same region, ensuring the application remains available even if an entire datacenter fails. Locally-Redundant Storage (LRS) only replicates within a single datacenter, so it cannot survive a full datacenter outage. On the AZ-900 exam, this scenario tests your understanding of the difference between intra-region resilience (ZRS) and cross-region disaster recovery (GRS). A common trap is choosing LRS because it is cheaper, but the question explicitly requires survival of an entire datacenter failure. Remember the memory tip: ZRS = Zone Redundant = Survives a Zone outage; LRS = Local Redundant = Survives only a local rack or drive failure.
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 is deploying a business-critical application on Azure virtual machines in the East US region. The application's managed disks must remain available even if an entire Azure datacenter experiences an outage. The company does not require cross-region disaster recovery. Which storage redundancy option should they select for the managed disks?
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 the East US region, ensuring the managed disks remain available even if an entire datacenter (one zone) fails. This meets the requirement for intra-region resilience without needing cross-region disaster recovery.
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 datacenter. This protects against hardware failures within the datacenter but does not protect against an entire datacenter outage. Therefore, it would not meet the requirement for availability if a datacenter fails.
- ✓
Zone-Redundant Storage (ZRS)
Why this is correct
ZRS replicates data synchronously across three Azure availability zones in the same region. If one zone (datacenter) goes down, the data remains available from the other zones. This is the correct choice for ensuring that managed disks survive a full datacenter failure within a single region.
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 for disaster recovery. However, GRS is not supported for Azure managed disks. It is designed for Azure storage accounts (blobs, files, queues, tables). Additionally, the requirement is only for within-region availability, not cross-region, so GRS would be overkill and unsupported.
- ✗
Read-Access Geo-Redundant Storage (RA-GRS)
Why it's wrong here
RA-GRS is similar to GRS but also allows read access to the data in the secondary region. Like GRS, it is not available for managed disks and is intended for storage accounts. It also provides cross-region protection, which is not needed here.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose LRS thinking it provides sufficient redundancy for high availability, but they overlook that LRS protects only against local hardware failures within a single datacenter, not an entire datacenter outage.
Trap categories for this question
Similar concept trap
RA-GRS is similar to GRS but also allows read access to the data in the secondary region. Like GRS, it is not available for managed disks and is intended for storage accounts. It also provides cross-region protection, which is not needed here.
Detailed technical explanation
How to think about this question
ZRS uses synchronous replication across availability zones, which are physically separate datacenters within the same Azure region, each with independent power, cooling, and networking. This provides a Recovery Point Objective (RPO) of zero and a Recovery Time Objective (RTO) typically within minutes for managed disks, as the data is always available in at least two other zones. In contrast, LRS offers no protection against a full datacenter failure, while GRS introduces asynchronous replication with a potential RPO of up to 15 minutes and requires a secondary region.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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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 the East US region, ensuring the managed disks remain available even if an entire datacenter (one zone) fails. This meets the requirement for intra-region resilience without needing cross-region disaster recovery.
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.
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
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