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

ApexGlow Media is designing a business continuity solution for its content delivery application. The application's metadata is stored in Azure Blob Storage. The primary region is East US, and the secondary region is West US. The design requirements are as follows:
- During normal operations, the application in the secondary region must have read-only access to the replicated metadata.
- In the event of a primary region outage, the application must be able to fail over to the secondary region and resume write operations.
- The Recovery Point Objective (RPO) must be less than 1515 minutes.
- The solution must minimize cost and avoid active-active compute configurations.

Which storage replication and failover design should you recommend?

  1. A
    Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS). In the event of a primary region outage, redirect the application's write operations directly to the secondary storage endpoint (−secondary.blob.core.windows.net-\text{secondary.blob.core.windows.net}) without initiating a failover.
  2. B
    Configure the storage account to use Geo-Redundant Storage (GRS). In the event of a primary region outage, direct the application in the secondary region to read from the secondary storage endpoint while waiting for Microsoft to perform an Azure-managed failover.
  3. Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS). In the event of a primary region outage, initiate a customer-managed failover, and then redirect the application's write operations to the primary storage endpoint.Answer
  4. D
    Configure the storage account to use Locally Redundant Storage (LRS) in the primary region. Use an Azure Function to asynchronously copy blobs to an LRS storage account in the secondary region to avoid geo-replication costs.

Answer

Configure the storage account to use Read-Access Geo-Redundant Storage (RA-GRS). In the event of a primary region outage, initiate a customer-managed failover, and then redirect the application's write operations to the primary storage endpoint.
The correct option satisfies the requirement of read access to the secondary region during normal operations by utilizing Read-Access Geo-Redundant Storage (RA-GRS). It also correctly handles the primary region outage by initiating a customer-managed failover, which promotes the secondary region to the new primary, changes the storage account replication to Locally Redundant Storage (LRS), and allows writes to proceed on the storage endpoint.

Step-by-Step Solution

1
Analyze read requirements during normal operations
Since read-only access to the secondary region is required during normal operations, Geo-Redundant Storage (GRS) is ruled out because it does not support reads from the secondary region unless a failover occurs. Read-Access Geo-Redundant Storage (RA-GRS) is required.
GRS keeps the secondary region completely offline to users until a failover, whereas RA-GRS provides a secondary endpoint for read access.
2
Evaluate write capabilities in the secondary region during an outage
Determine that write operations cannot be directed to the secondary endpoint directly because RA-GRS only supports read access on the secondary endpoint prior to failover.
Directing writes to the secondary endpoint before failover results in write failures.
3
Determine the correct failover strategy to enable writes
Initiate a customer-managed failover. This action promotes the secondary region to become the new primary region, switches the storage configuration to Locally Redundant Storage (LRS), and enables write access on the primary endpoint.
Customer-managed failover is required to swap the primary and secondary roles and allow write operations to resume on the storage account.

Key Concept

Azure Storage Geo-Replication Failover Behavior
Estimated Time:2m 0s
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Topics

Design Storage and Non-Relational Data HA and DR

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