Locally redundant storage (LRS) replicates your data within the region in which you created your storage account. To maximize durability, every request made against data in your storage account is replicated three times. These three replicas each reside in separate fault domains and upgrade domains. A fault domain (FD) is a group of nodes that represent a physical unit of failure and can be considered as nodes belonging to the same physical rack. An upgrade domain (UD) is a group of nodes that are upgraded together during the process of a service upgrade (rollout). The three replicas are spread across UDs and FDs to ensure that data is available even if hardware failure impacts a single rack and when nodes are upgraded during a rollout. A request returns successfully only once it has been written to all three replicas.
While geo-redundant storage (GRS) is recommended for most applications, locally redundant storage may be desirable in certain scenarios:
- LRS is less expensive than GRS, and also offers higher throughput. If your application stores data that can be easily reconstructed, you may opt for LRS.
- Some applications are restricted to replicating data only within a single region due to data governance requirements.
- If your application has its own geo-replication strategy, then it may not require GRS.
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