AZ-900 Describe Azure architecture and services Practice Question
A company runs a critical transaction-processing application on Azure virtual machines in the East US region. The application writes data to Azure managed disks and also stores files in Azure Blob Storage. The company's disaster recovery policy requires that all storage data must survive a complete failure of an Azure availability zone within the same region without any data loss. The solution must use synchronous replication and must not replicate data to a different Azure region. Which Azure storage redundancy option should the company configure for the Blob Storage account?
⚠ Common exam trap
Test-takers frequently confuse ZRS with LRS, assuming LRS provides zone-level resilience, or mistakenly choose GRS/RA-GRS because they think geo-replication is required for disaster recovery, ignoring the explicit synchronous and intra-region constraints.
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 same region, ensuring no data loss if an entire zone fails. This meets the disaster recovery requirement for synchronous replication and intra-region resilience without replicating to a different region.
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 location in the primary region. This protects against server rack and drive failures, but not against a failure of an entire availability zone, because all replicas reside in the same datacenter.
When this WOULD be correct
A company runs a non-critical application on a single VM in a region without availability zones, and the disaster recovery policy only requires protection against local hardware failures (e.g., disk or server failure) within the same datacenter, with no need for zone or region redundancy.
- ✓
Zone-redundant storage (ZRS)
Why this is correct
ZRS replicates data synchronously across three Azure availability zones within the primary region. This ensures that if one zone fails, the data remains available and durable from the other zones, meeting the requirement for zone-level protection without cross-region replication.
- ✗
Geo-redundant storage (GRS)
Why it's wrong here
GRS asynchronously replicates data from the primary region to a secondary region hundreds of miles away. While this provides disaster recovery across regions, it does not meet the requirement to remain within the same region, and the asynchronous replication means there could be some data loss if a regional disaster occurs.
When this WOULD be correct
A company requires disaster recovery that can withstand a complete regional outage and is willing to accept asynchronous replication. The question would specify that data must survive a region-level failure and cross-region replication is allowed.
- ✗
Read-access geo-redundant storage (RA-GRS)
Why it's wrong here
RA-GRS is identical to GRS but additionally provides read access to the data in the secondary region. It also uses asynchronous replication and replicates to a different region, which does not fulfill the stated requirement of staying within the same region and using synchronous replication.
When this WOULD be correct
A company requires disaster recovery across Azure regions with asynchronous replication to protect against a region-wide outage. The application can tolerate some data loss (e.g., a few minutes) and needs read access to the secondary region during normal operations.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Zone-redundant storage (ZRS)Correct answer▾
Why this is correct
ZRS replicates data synchronously across three Azure availability zones within the primary region. This ensures that if one zone fails, the data remains available and durable from the other zones, meeting the requirement for zone-level protection without cross-region replication.
✗Locally redundant storage (LRS)Wrong answer — click to see why▾
Why this is wrong here
LRS replicates data three times within a single availability zone, so a complete zone failure would cause data loss, violating the requirement for survival of a zone failure with synchronous replication.
★ When this WOULD be the correct answer
A company runs a non-critical application on a single VM in a region without availability zones, and the disaster recovery policy only requires protection against local hardware failures (e.g., disk or server failure) within the same datacenter, with no need for zone or region redundancy.
Why candidates choose this
Candidates may think LRS is sufficient because it provides three copies within a datacenter, overlooking that the question explicitly requires survival of a full availability zone failure, which LRS cannot withstand.
✗Geo-redundant storage (GRS)Wrong answer — click to see why▾
Why this is wrong here
Geo-redundant storage (GRS) replicates data to a secondary region, which violates the requirement that data must not be replicated to a different Azure region. Additionally, GRS uses asynchronous replication, not synchronous.
★ When this WOULD be the correct answer
A company requires disaster recovery that can withstand a complete regional outage and is willing to accept asynchronous replication. The question would specify that data must survive a region-level failure and cross-region replication is allowed.
Why candidates choose this
Candidates may confuse disaster recovery requirements with geo-redundancy, assuming that any disaster scenario requires a secondary region, and overlook the specific constraints of same-region and synchronous replication.
✗Read-access geo-redundant storage (RA-GRS)Wrong answer — click to see why▾
Why this is wrong here
Geo-redundant storage (GRS) replicates data to a paired secondary region, which violates the requirement to not replicate data to a different Azure region. Additionally, GRS uses asynchronous replication, not synchronous.
★ When this WOULD be the correct answer
A company requires disaster recovery across Azure regions with asynchronous replication to protect against a region-wide outage. The application can tolerate some data loss (e.g., a few minutes) and needs read access to the secondary region during normal operations.
Why candidates choose this
Candidates may confuse 'geo-redundant' with 'zone-redundant' or think that any redundancy beyond LRS automatically meets disaster recovery needs, overlooking the specific constraints of same-region and synchronous replication.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
Key term
Region
A region is a distinct geographic location where a cloud provider operates multiple data centers that are connected by low-latency networks and provide cloud services.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.