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Difficulty: HardData Redundancy and High Availability

An enterprise is designing the storage architecture for two new applications:

1. App1 stores high-throughput transactional logging data using a Premium Block Blob storage account. It requires sub-millisecond write latency and must tolerate the loss of a single datacenter facility within the primary region without any data loss or application downtime.
2. App2 stores client documents in a Standard General Purpose v2 (GPv2) storage account. It must remain online and survive the failure of an entire availability zone in the primary region with zero recovery time. Additionally, the application must support read-only access to a secondary region for reporting purposes during normal operations.

Which two redundancy configurations should you recommend to meet these requirements?

  1. Zone-redundant storage (ZRS) for App1Answer
  2. B
    Locally-redundant storage (LRS) for App1
  3. Read-access geo-zone-redundant storage (RA-GZRS) for App2Answer
  4. D
    Read-access geo-redundant storage (RA-GRS) for App2

Answer

Zone-redundant storage (ZRS) for App1 and Read-access geo-zone-redundant storage (RA-GZRS) for App2
The correct configurations are Zone-redundant storage (ZRS) for App1 and Read-access geo-zone-redundant storage (RA-GZRS) for App2. App1 utilizes the Premium Block Blob tier, which supports only LRS and ZRS. To handle a physical datacenter failure in the primary region, ZRS is required. App2 requires high availability across zones in the primary region alongside read access to a secondary region, which requires RA-GZRS.

Step-by-Step Solution

1
Analyze the App1 storage type and resiliency requirements.
App1 uses Premium Block Blob storage. Premium tier blob storage only supports Locally-redundant storage (LRS) and Zone-redundant storage (ZRS). To survive the loss of a single datacenter facility, Zone-redundant storage (ZRS) is required.
LRS does not survive a datacenter facility outage, and geo-redundancy options are not available in the Premium Block Blob tier.
2
Analyze the App2 storage type and resiliency requirements.
App2 uses Standard GPv2 storage, requires zonal resilience (survive a zone outage in the primary region), and must support read-only secondary access.
Read-access geo-zone-redundant storage (RA-GZRS) combines zonal redundancy in the primary region with geo-replication and read-only secondary endpoints. Read-access geo-redundant storage (RA-GRS) only uses LRS in the primary region, meaning it cannot survive a primary zone failure without manual/automatic failover (violating the zero recovery time requirement).

Key Concept

Selecting Azure Storage redundancy options based on performance tiers, zonal availability, and cross-region read access.
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Topics

Data Redundancy and High Availability

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