A dataset must survive the loss of one datacentre in its primary region without anybody performing a failover, and regulation forbids a copy of it leaving that region. Which redundancy option meets both requirements?

Microsoft Certified: Azure Fundamentals (AZ-900), objective architecture-and-services. Azure architecture and services medium

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The options

Correct Zone-redundant storage

Correct. It writes three copies synchronously across three availability zones inside the primary region, so losing one zone is transparent to the application and nothing leaves the region.

Not correct Locally redundant storage

Wrong. It keeps three copies, but all of them inside a single datacentre, so the one failure the requirement names takes all three at once.

Not correct Geo-redundant storage

Wrong on residency. It copies the data asynchronously to the paired region — precisely the copy leaving the region that regulation forbids — and recovering from that copy involves a failover rather than being transparent.

Not correct Read-access geo-redundant storage

Wrong for the same reason as geo-redundant storage, and it widens the problem: the out-of-region copy is now readable, so there is more of the thing the regulator objected to, not less.

Why

Count the copies, then ask where they are. Locally redundant keeps three in one datacentre; zone-redundant spreads three across zones in the region, written synchronously; geo-redundant adds an asynchronous copy in the paired region; geo-zone-redundant combines both. The synchronous-versus-asynchronous distinction matters as much as the geography: in-region replication is complete before the write is acknowledged, cross-region replication is not, so a regional failover can lose the most recent writes.

Where this comes from

Cited
Microsoft AZ-900 study guide skill area architecture-and-services.storage

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