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Difficulty: HardData Redundancy and High Availability

A financial services firm is designing the storage infrastructure for a new document archiving system. The system will store critical customer statements as Block Blobs in a general-purpose v2 storage account. The design must satisfy the following technical requirements:

- The storage solution must withstand the complete failure of an Azure availability zone in the primary region without any data loss or read/write service disruption.
- To protect against a regional disaster, the data must be replicated to a secondary paired region.
- In the event of a primary region outage, the application must be able to immediately read the archived documents from the secondary region without initiating a storage account failover and without waiting for Microsoft to declare a disaster.

Which redundancy option should you select for the storage account?

  1. Read-Access Geo-Zone-Redundant Storage (RA-GZRS)Answer
  2. B
    Geo-Zone-Redundant Storage (GZRS)
  3. C
    Read-Access Geo-Redundant Storage (RA-GRS)
  4. D
    Zone-Redundant Storage (ZRS)

Answer

Read-Access Geo-Zone-Redundant Storage (RA-GZRS)
Read-Access Geo-Zone-Redundant Storage (RA-GZRS) is correct because it uses Zone-Redundant Storage (ZRS) in the primary region to survive a zone outage, replicates the data asynchronously to a secondary region for disaster recovery, and provides a read-only endpoint in the secondary region that is available immediately without initiating a failover.

Step-by-Step Solution

1
Analyze primary region availability requirements.
The requirement to survive a complete availability zone outage in the primary region without service disruption rules out Locally Redundant Storage (LRS) and replication options built on LRS, such as Read-Access Geo-Redundant Storage (RA-GRS). It leaves Zone-Redundant Storage (ZRS), Geo-Zone-Redundant Storage (GZRS), and Read-Access Geo-Zone-Redundant Storage (RA-GZRS) as candidates.
Zonal redundancy is necessary to ensure that data remains online and accessible even if one of the physical datacenters housing the availability zone fails.
2
Analyze regional disaster recovery requirements.
The requirement to replicate data to a secondary region rules out Zone-Redundant Storage (ZRS), which is confined to the primary region. This leaves Geo-Zone-Redundant Storage (GZRS) and Read-Access Geo-Zone-Redundant Storage (RA-GZRS).
Cross-region replication is required to achieve recovery and durability in a secondary region in the event of a disaster affecting the primary region.
3
Analyze secondary region read requirements and failover constraints.
The requirement to read data immediately from the secondary region without initiating a failover or waiting for Microsoft to declare a disaster rules out Geo-Zone-Redundant Storage (GZRS), leaving Read-Access Geo-Zone-Redundant Storage (RA-GZRS) as the only viable option.
Standard geo-redundant options require a failover to switch primary endpoints before the secondary region is readable. Only read-access options (RA-GRS/RA-GZRS) expose a permanent secondary read-only endpoint (-secondary) that applications can query at any time.

Key Concept

Selecting Azure Storage redundancy tiers to meet combined availability, regional disaster recovery, and read-access requirements.
Estimated Time:2m 0s
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Topics

Data Redundancy and High Availability

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