Azure Storage Accounts is a service that offers customers to store blobs, files, queues and tabels for applications running. Storage Accounts are highly scaleable and can go up to Petabyte of data storages.
Storage Account customers can use the feature of redundancy when we create an account (can change to different replication). Default its configured for LRS (Local Redundant Storage), for more follow here.
If the storage replication method is configured to GRS or RA-GRS customers of Azure Storage Account can leverage the storage account failover feature which is public preview. Before introducing this feature if the primary storage account inaccessible we need to go through Microsoft for failover to secondary copy. But with this feature we can manage the failover to secondary location by ourselves, if the primary was unavailable.

Account failover is supported in preview for new and existing Azure Resource Manager storage accounts that are configured for RA-GRS and GRS. Storage accounts may be general-purpose v1 (GPv1), general-purpose v2 (GPv2), or Blob Storage accounts. Account failover is currently supported in US-West 2 and US-West Central.
To configure we need to follow below steps.
Convert the Storage Account Replication method to GRS or RA-GRS
Navigate SA, Select configuration then change replication.

Storage Replication feature still on a preview stage and to test, first we need to enable the feature through PowerShell. Connect to Azure from Powershell, run following command. To approve the preview it will take 1-2 days.
#Register for the feature
Register-AzureRmProviderFeature -FeatureName CustomerControlledFailover -ProviderNamespace Microsoft.Storage
#To see the Status of the feature enable
Get-AzureRmProviderFeature -FeatureName CustomerControlledFailover -ProviderNamespace Microsoft.Storage
If the registration was successful we can see it in PowerShell as below

Before we go through process please refer the documentation. As this is still in public preview we are not recommending this to use for production applications.
After successful registration of the feature, in Storage Account blade we can find the tab for Geo-Replication as below.

To failover from primary to secondary we need to click Prepare for Failover.

Confirm the failover process

When we confirm the failover it will process failover as below

After failover we can see that secondary region becomes primary.

Now we can use new storage account endpoints to our application.
Public Preview Announcement.