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Difficulty: MediumDesign Storage and Non-Relational Data HA and DR

SolisTransport is designing a disaster recovery and business continuity solution for its maritime cargo tracking system. The tracking system writes voyage telemetry logs to a general-purpose v2 storage account in the East US region.

The solution must meet the following requirements:
- Recovery Point Objective (RPO): Under 15 minutes.
- Recovery Time Objective (RTO) for reads: Near 0 minutes. The application must be able to read tracking data from a secondary region (West US) immediately during a primary region outage, without waiting for Microsoft to declare a disaster or initiate a failover.
- Write Availability: Write capability in the secondary region is only required if the outage is prolonged and a failover is officially declared.
- Cost Constraints: Minimize storage costs and avoid the overhead of zone redundancy in the primary region.

Which storage configuration and recovery strategy should you recommend?

  1. Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS). Direct read requests to the secondary endpoint during the outage, and initiate a customer-managed failover if write capability is required.Answer
  2. B
    Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS). Direct write requests to the secondary endpoint during the outage, as RA-GRS supports active-active writes without initiating a failover.
  3. C
    Configure the storage account to use Geo-Redundant Storage (GRS). Direct read requests to the secondary endpoint during the outage, and initiate a customer-managed failover if write capability is required.
  4. D
    Configure the storage account to use Locally Redundant Storage (LRS). In the event of an outage, restore the storage account from an Azure Backup vault to a new storage account in the West US region.

Answer

Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS), direct read requests to the secondary endpoint during the outage, and initiate a customer-managed failover if write capability is required.
The correct configuration uses Read-Access Geo-Redundant Storage (RA-GRS). RA-GRS provides a secondary read-only endpoint that allows the application to read the tracking data immediately during a primary outage, meeting the near-zero RTO requirement. It only supports write operations to the secondary region after a customer-managed failover is triggered, which meets the requirement of allowing writes only when a failover is officially declared. Furthermore, RA-GRS uses locally redundant storage (LRS) in both the primary and secondary regions, satisfying the cost constraint of avoiding zone-redundancy overhead in the primary region.

Step-by-Step Solution

1
Evaluate read availability requirements during a primary region outage.
The RTO for reads must be near 0 minutes without waiting for a failover, which means the secondary region must be readable. This requires a read-access geo-redundant option (RA-GRS or RA-GZRS), ruling out standard GRS and LRS.
Standard GRS does not expose a secondary read endpoint until failover occurs.
2
Evaluate write availability and failover requirements.
Writes to the secondary region are only needed if a failover is declared. Prior to failover, writes must not go to the secondary endpoint because it is read-only.
Both GRS and RA-GRS secondary endpoints do not support writes before failover.
3
Evaluate cost and zone-redundancy constraints.
The requirements specify minimizing costs and avoiding zone redundancy in the primary region. This rules out RA-GZRS (which uses zone redundancy in the primary region) in favor of RA-GRS (which uses local redundancy in both primary and secondary regions).
RA-GRS is the most cost-effective option that satisfies the geo-redundant read availability requirements.

Key Concept

Azure Storage replication options, focusing on the differences between GRS and RA-GRS, read/write endpoint availability, and the failover process.
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Topics

Design Storage and Non-Relational Data HA and DR

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