AZ-900: Redundancy Options in Azure Storage

Redundancy in Azure Storage ensures your data remains available and durable, even in the case of hardware or regional failures. Azure offers a range of redundancy options that replicate your data within a region or across regions.

Redundancy Within a Primary Region

Locally Redundant Storage (LRS)

• Three copies of your data are made within a single physical location.
• Protects against rack and drive-level failures.
• Provides 99.999999999% durability (11 nines) over a given year.
• This is the lowest-cost redundancy option.
• Best suited for non-critical data that can be easily recreated.
• Not recommended for high availability or resilience against site-level disasters like fire or flooding.
• Commonly used for: Blob, queue, and table storage, managed disks, and Azure Files.
• Compatible with Standard general-purpose v2, Premium block blobs, and Premium file shares.

Zone-Redundant Storage (ZRS)

• Your data is replicated across three Azure availability zones.
• Each zone has independent power, cooling, and networking.
• Offers 99.9999999999% durability (12 nines).
• Good for low latency and high-performance workloads.
• Does not protect against a complete regional disaster.
• Supported only on standard general-purpose v2 accounts.
• Synchronous replication ensures that all zones receive the data at the same time.

Redundancy Across Regions (Geo-replication)

Azure can also replicate your data to a secondary paired region, chosen by Microsoft, that is typically hundreds of miles away.

Geo-Redundant Storage (GRS)

• Copies data three times in the primary region (using LRS), then replicates it to a secondary region.
• Offers 99.99999999999999% durability (16 nines).
• Supported by general-purpose v1 and v2 accounts, and legacy blob storage.
• Not suitable for Azure managed disks.

Geo-Zone-Redundant Storage (GZRS)

• Combines ZRS in the primary region and LRS in the secondary.
• Ensures synchronous replication within the primary region and asynchronous replication to the secondary region.
• Offers maximum durability and availability.
• Recommended for mission-critical applications.
• Only supported on standard general-purpose v2 accounts.

Recovery & Read Access

• By default, the secondary region is not accessible.
• You can enable read-access with RA-GRS or RA-GZRS.
• Note: Read access is not available for Azure Files.
• Secondary endpoints include -secondary in the URL.
• In the event of a failure, you can perform a failover.
• The secondary becomes your new primary region.
• Azure’s Recovery Point Objective (RPO) is typically less than 15 minutes, increasing the reliability of your Azure Storage.

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To understand Azure storage durability and availability in greater detail, watch our AZ-900 video course for real-world examples and insights. Alternatively, please go back to our list of AZ-900 requirements.

Please click here to find out more about Microsoft’s AZ-900 exam.