MSDEVBUILD / azure

Storage Redundancy: LRS, ZRS, GRS, GZRS

Primary regionZone 1Zone 2Zone 3Secondary regionLRS: 3 copies, 1 datacenterZRS: across 3 zonesGRS / GZRS: + another region
Watch the copies appear: one datacenter, three zones, then another region for maximum safety.

😟 THE PROBLEM

One datacenter incident could make critical data unavailable or lost.

😊 THE SOLUTION

Choose the right redundancy: ZRS for zones, GZRS for regions too.

  • Datacenter failure✓ ZRS copies across zones
  • Regional disaster✓ GRS / GZRS copy to another region
  • Need to read during an outage✓ RA-GRS / RA-GZRS
🛠️ Solved with: LRS · ZRS · GRS · GZRS
Try it yourself in the Azure simulator No Azure account needed. Storage accounts and redundancy 🗄️ Try it ❯
Module 2: Architecture & Services ⏱ 7 min read Updated 11 Nov 2026

Quick answer

Azure Storage always keeps multiple copies of your data. LRS keeps three copies in one datacenter. ZRS keeps three copies across three availability zones. GRS keeps three copies locally plus three in a secondary region. GZRS combines ZRS in the primary region with a copy in a secondary region. RA-GRS and RA-GZRS also let you read from the secondary region.

Exam objective: 2.3.3 Describe redundancy options. (Skills measured as of July 20, 2026)

Start with a question

If a datacenter burns down tonight, are your customers’ photos gone?

It depends on the redundancy you picked when you created the storage account.

Explain it like I’m 10

The technical explanation

OptionCopiesSurvivesRead secondary?
LRS3 in one datacenterDisk and rack failures–
ZRS3 across 3 zonesDatacenter failure–
GRS3 local + 3 in secondary regionRegional disasterRA-GRS
GZRS3 across zones + 3 in secondary regionDatacenter and regional disastersRA-GZRS

Real-world business scenario

Healthcare

A hospital records system

The problem
Medical images were on LRS; a risk review found a single datacenter incident could make them unavailable.
What they used
Switched to RA-GZRS.
Why that choice
Zone redundancy for local resilience plus a readable copy in another region.
The result
Images remain available during datacenter incidents and readable in a regional outage.

When to use it and when not to

✓ Use it when…

  • **LRS** for easily re-creatable or dev data.
  • **ZRS** for high availability in one region.
  • **GZRS** for critical data that must survive regional disasters.

✕ Think twice when…

  • Paying for geo-redundancy on temporary data you can rebuild.
Ready for more?The full lesson adds the technical explanation, when to use it, interview questions and revision notes.

Interview preparation

Say your answer out loud first, then open the model answer. Interviewers care more about your reasoning than the exact words.

Beginner What is the difference between LRS and ZRS?

Model answer

LRS keeps three copies in one datacenter, protecting against disk or rack failures. ZRS spreads three copies across availability zones, so data survives a whole datacenter failure.

Intermediate When would you choose GZRS?

Model answer

When data must survive both a datacenter failure (zones) and a regional disaster (secondary region). It suits critical data with high availability needs. Add RA- if applications must read from the secondary during an outage.

Experienced developer What should you know about the secondary region copy?

Model answer

Replication to the secondary is asynchronous, so the latest writes may be lost in a disaster. The recovery point is not zero. Without RA-, the secondary is not readable until a failover. After a customer-initiated failover, the account becomes LRS in the new primary until you reconfigure it.

Test yourself with exercises

3 original practice questions in the AZ-900 style. Pick your answers, then check them. You will see why each option is right or wrong. Score 75% or more and this topic is marked complete.

Question 1

Question 1 of 3

Which redundancy option keeps three copies in a single datacenter?

Question 2

Question 2 of 3

Data must survive a datacenter failure but stay within one region. Which option?

Question 3

Question 3 of 3 · Select 2

Which TWO options copy data to a secondary region?

Quick revision

Key points

  • LRS = 3 copies, 1 datacenter (cheapest).
  • ZRS = 3 copies across 3 zones.
  • GRS = LRS + secondary region.
  • GZRS = ZRS + secondary region (highest protection).
  • RA- variants allow reading from the secondary.

Important terminology

LRS
Locally redundant storage. 3 copies in one datacenter.
ZRS
Zone-redundant storage. 3 copies across 3 availability zones.
GRS
Geo-redundant storage. LRS plus asynchronous copy to a secondary region.
GZRS
Geo-zone-redundant storage. ZRS plus asynchronous copy to a secondary region.
RA-
Read access to the secondary region at all times (RA-GRS, RA-GZRS).

Common mistakes

  • Thinking LRS protects against a datacenter fire. It does not.

Exam tips

  • "Survive a datacenter failure but stay in one region" = ZRS.
  • "Survive a regional outage" = GRS or GZRS.

Five quick revision questions

  1. 1.How many copies does LRS keep?Show

    Three, in one datacenter.

  2. 2.Which option spreads copies across availability zones?Show

    ZRS (and GZRS in the primary region).

  3. 3.Which options copy data to a secondary region?Show

    GRS and GZRS (and their RA- variants).

  4. 4.What does RA- add?Show

    Read access to the secondary region.

  5. 5.Is replication to the secondary region synchronous?Show

    No, it is asynchronous.

Official references

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