Customer-managed unplanned failover now supports Azure Data Lake Storage and SSH File Transfer Protocol in General Availability
We are excited to announce the General Availability of customer managed unplanned failover for Azure Data Lake Storage and storage accounts with SSH File Transfer Protocol (SFTP) enabled.
What is Unplanned Failover?
With customer managed unplanned failover, you are in control of initiating your failover. Unplanned failover allows you to switch your storage endpoints from the primary region to the secondary region. During an unplanned failover, write requests are redirected to the secondary region, which then becomes the new primary region.
Because an unplanned failover is designed for scenarios where the primary region is experiencing an availability issue, unplanned failover happens without the primary region fully completing replication to the secondary region. As a result, during an unplanned failover there is a possibility of data loss. This loss depends on the amount of data that has yet to be replicated from the primary region to the secondary region. Each storage account has a ‘last sync time’ property, which indicates the last time a full synchronization between the primary and the secondary region was completed. Any data written between the last sync time and the current time may only be partially replicated to the secondary region, which is why unplanned failover may incur data loss.
Unplanned failover is intended to be utilized during a true disaster where the primary region is unavailable. Therefore, once completed, the data in the original primary region is erased, the account is changed to locally redundant storage (LRS) and your applications can resume writing data to the storage account.
If the previous primary region becomes available again, you can convert your account back to geo-redundant storage (GRS). Migrating your account from LRS to GRS will initiate a full data replication from the new primary region to the secondary which has geo-bandwidth costs. If your scenario involves failing over while the primary region is still available, consider planned failover.
Planned failover can be utilized in scenarios including planned disaster recovery testing or recovering from non-storage related outages. Unlike unplanned failover, the storage service endpoints must be available in both the primary and secondary regions before a planned failover can be initiated. This is because planned failover is a 3-step process that includes: (1) making the current primary read only, (2) syncing all the data to the secondary (ensuring no data loss), and (3) swapping the primary and secondary regions so that writes are now in the new region. In contrast with unplanned failover, planned failover maintains the geo-redundancy of the account so planned failback does not require a full data copy.
To learn more about planned failover and how it works view, Public Preview: Customer Managed Planned Failover for Azure Storage | Microsoft Community Hub
To learn more about each failover option and the primary use case for each view, Azure storage disaster recovery planning and failover - Azure Storage | Microsoft Learn
How to get started?
Getting started is simple, to learn more about the step-by-step process to initiate an unplanned failover review the documentation: Initiate a storage account failover - Azure Storage | Microsoft Learn
Feedback
If you have questions or feedback, reach out at storagefailover@service.microsoft.com
Updated Jan 17, 2025
Version 1.0imanihall
Microsoft
Joined June 03, 2024
Azure Storage Blog
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