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LRS Redundancy vs ZRS Redundancy

Azure Storage always stores multiple copies of your data so that it is protected from planned and unplanned events, including transient hardware failures, network or power outages, and massive natural disasters. Redundancy ensures that your storage account meets its availability and durability targets even in the face of failures.


In this lecture, the focus is on understanding the key differences between Locally Redundant Storage (LRS) and Zone Redundant Storage (ZRS) within Azure Storage services. The discourse begins with an overview of the importance of redundancy in protecting data from various types of failures and outages, ranging from hardware malfunctions to natural disasters.

The lecture progresses to emphasize the significance of redundancy for ensuring the availability and durability of storage accounts in Azure. There is an exploration of the considerations that must be taken into account when selecting a redundancy option, such as cost versus availability, and the need for replication within or across regions based on the business requirements.

The different components of Azure storage services are then highlighted, and it is explained that a storage account serves as a shared pool from which various storage resources are deployed. These resources include blob containers, file shares, tables, and queues. It is underscored that the redundancy option chosen for a storage account applies to all services within that account, and different redundancy requirements necessitate separate storage accounts.

The lecture delves into LRS, explaining how it replicates data synchronously three times within a single data center in the primary region, offering 11 nines of durability annually. While LRS is the most cost-effective option, it also presents the lowest level of durability and only protects against specific types of failures like server rack or drive failures. LRS is suitable for data that can be reconstructed or for compliance with regional data replication laws.

Next, ZRS is introduced, which replicates data across three separate physical locations, each with its own power, cooling, and networking, within the primary region. This offers a higher level of durability—12 nines annually—and maintains data accessibility even if one zone is compromised. The synchronization of data is done across all three zones before a write operation is considered successful. ZRS is recommended for high availability requirements, data governance within a region, and Azure Files workloads.

The discussion includes practical advice for how to apply this knowledge in an exam context, suggesting that students remember the definitions of LRS and ZRS, the availability of each, the Azure storage types that support them, their typical use cases, and that LRS is the most affordable option. The lecture ultimately prepares students to make informed decisions regarding the redundancy options for Azure Storage based on specific needs and scenarios.

© 2023 Thomas J Mitchell / TomTeachesIT