AZ-900 Describe Azure architecture and services Practice Question
Which Azure storage redundancy option replicates data across multiple availability zones within a single region?
⚠ Common exam trap
Many exam-takers confuse 'zone' with 'region' and incorrectly choose GRS or RA-GRS, thinking that 'redundancy across zones' means across regions, or they pick LRS because they assume 'local' implies zone-level redundancy.
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) is the correct answer because it synchronously replicates data across three Azure availability zones within a single region, ensuring durability even if an entire zone fails. This provides higher availability than LRS (which replicates within a single data center) and lower latency than GRS/RA-GRS (which replicate to a secondary 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
Locally Redundant Storage (LRS) replicates your data three times synchronously within a single physical data center in the chosen region. It protects against drive failures and server rack outages, but if that entire data center — or the single availability zone it lives in — goes down, your data becomes unavailable. Because LRS does not span multiple availability zones, it cannot satisfy a requirement for zone-redundant storage.
- ✗
Geo-Redundant Storage (GRS)
Why it's wrong here
Geo-Redundant Storage (GRS) asynchronously copies data to a paired secondary region located hundreds of miles away to protect against region-wide outages. However, within the primary region, GRS uses LRS — three copies in one data center — and does not replicate across availability zones. Thus, it offers geographic redundancy, not the specifically requested zonal redundancy.
- ✓
Zone-Redundant Storage (ZRS)
Why this is correct
Zone-Redundant Storage (ZRS) synchronously replicates your data across three distinct availability zones within the same Azure region. Each zone is an isolated location with independent power, cooling, and networking, so ZRS remains available through a single data-center failure. This is the correct answer because it specifically provides redundancy across availability zones, not just within one data center or across a paired region.
- ✗
Read-Access Geo-Redundant Storage (RA-GRS)
Why it's wrong here
Read-Access Geo-Redundant Storage (RA-GRS) replicates data asynchronously to a paired secondary region and additionally provides read access to that region's copy. The primary region's redundancy is based on LRS, not ZRS, so the answer is wrong: it offers cross-region protection, not zone-level redundancy within a single region, and it writes are not synchronous across three zones.
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Zone-redundant storage
Zone-redundant storage is a data replication method that stores copies of your data in multiple physical locations within a cloud region, so your data remains safe and available even if one entire data center fails.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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