Overview Of Azure LRS, ZRS, GRS - RA GRS


Before we start with the understanding of what is Azure LRS, ZRS, GRS – RA GRS, we should know:
  1. Basic knowledge of cloud computing and its services
  2. Basic knowledge of Microsoft Azure
  3. Good to have knowledge of high availability applications


In this article, we will explore what is Microsoft Azure LRS, ZRS, GRS – RA GRS. However, before we look into it, let’s understand this:
Microsoft Azure cloud provider has data centers over all the world within different regions. Every region can have one or multiple zones and they are isolated from each other. Each zone can have one or more multiple data centers with independent power, cooling, and networking. This is much needed for critical workloads with compliance, decreasing latency, and data authority requirements. Admin can move resources of applications within zones in the case of an outage.
Now think about if Microsoft data center goes does down, what happens if the entire region and their data centers go down? What will happen in case of disasters? We need to take these cases under consideration while designing the critical applications where we need high availability of applications.
To solve this business problem Azure locally redundant storage (LRS), zone-redundant storage (ZRS), Geo-redundant storage (GRS), Read-access geo-redundant storage (RA-GRS) helps us.

What is Azure LRS, ZRS GRS – RA GRS

Azure Storage
  • In simple words, it is Microsoft’s cloud storage. It has a wide variety of different types of cloud storage depending upon the data object to store. We can store text, binary data, files/documents, messaging contents, NoSQL, etc.
  • Benefits - Azure cloud storage is highly available, secure, tremendous scalable, accessible over HTTP/HTTPS, etc.
  • Azure Blobs, Azure Files, Azure Queues and Azure tables are the different services coming under the Azure storage services.
The data in your Microsoft Azure storage account is always replicated to ensure durability and high availability. It protects our data from any type of failures like - Fault domain - refers to unexpected hardware failure, update domain - refers to predetermined software updates on Azure., disasters, etc.
In the Azure cloud, we have the choice to replicate our data within the same data center, across zonal data centers in the same region or different regions. Azure storage regularly verifies the integrity of data using cyclic redundancy checks (CRCs). If it is corrupted, then it's recovered using redundant data.
Azure storage maintains at least 3 replicas of our data wither within the same data center using locally redundant storage (LRS), or secondary data center either in zone-redundant storage (ZRS), geo-redundant storage (GRS), or read-access geo-redundant storage (RA-GRS). With this, Azure preserves our application up-time in the case of failures.
  1. Locally redundant storage (LRS)
    It helps to replicate our data in the same data center, and it is a low-cost data redundancy technique. LRS is the lowest-cost replication option and offers the least durability compared to other options. It provides at least 99.999999999% (11 nines) durability of objects over a given year.

    This is helpful when we can easily reconstruct the data in case of data loss, or we have restricted data to replicate only within the country/region.

  2. Zone-redundant storage (ZRS)
    It helps us for excellent performance, low latency and replicate our data synchronously across three storage clusters in a single region. Each storage cluster is physically separated but within the same region. ZRS offers durability for storage objects of at least 99.9999999999% (12 9's) over a given year.

  3. Geo-redundant storage (GRS)
    As I explained above it helps us in replicating our data to another region which is far away hundreds of miles away from the primary region. It provides at least 99.99999999999999% (16 9's) durability of objects over a given year. GRS replicates our data to another region, but data will be available to be read-only if Microsoft initiates a failure from primary to the secondary region.

  4. Read-access geo-redundant storage (RA-GRS)
    It is based on the GRS, but it also provides an option to read from the secondary region, regardless of whether Microsoft initiates a failover from the primary to the secondary region.
Image Source – Microsoft Docs
Migrating to or from LRS, GRS, and RA-GRS is straightforward – we can use the Azure portal or the Storage Resource Provider API to change your account's redundancy type.
Reference Links
  • https://docs.microsoft.com/en-us/azure/storage/common/storage-introduction
  • https://docs.microsoft.com/en-us/azure/storage/common/storage-redundancy-grs
  • https://docs.microsoft.com/en-us/azure/storage/common/storage-redundancy-lrs?toc=%2fazure%2fstorage%2fblobs%2ftoc.json
  • https://docs.microsoft.com/en-us/azure/storage/common/storage-designing-ha-apps-with-ragrs?toc=%2fazure%2fstorage%2fblobs%2ftoc.json
  • https://docs.microsoft.com/en-us/azure/storage/common/storage-introduction


In this article, we have looked at an overview of Azure LRS, ZRS, GRS – RA GRS.

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