Revise storage and resiliency information for backups

Updated storage and resiliency details for Managed Disk incremental snapshots, including ZRS support and conditions for new Backup Instances.

Author: rohan-sahini

articles/backup/azure-elastic-san-backup-overview.md

@@ -25,7 +25,10 @@ Elastic SAN backup includes the following key features:
 
 - **Region availability**: The feature is currently [available in specific regions](azure-elastic-storage-area-network-backup-support-matrix.md#supported-regions) only. 
 - **Snapshot export**: Exports the selected Elastic SAN to an independent managed disk incremental snapshot (operational tier) at a given point in time.
-- **Storage and resiliency**: Managed Disk incremental snapshot is stored in Locally redundant storage (LRS) resiliency (in LRS-[supported regions](azure-elastic-storage-area-network-backup-support-matrix.md#supported-regions)), independent of the Elastic SAN lifecycle.
+- **Storage and resiliency**: Managed Disk incremental snapshot can be stored in Zonally redundant storage (ZRS) or Locally redundant storage (LRS) resiliency (in supported regions), independent of the Elastic SAN lifecycle.
+
+   >[!Note]
+   >ZRS snapshot storage applies only to new Backup Instances created in regions where ZRS is supported, and only when there is no Managed Disk incremental snapshot already exported from the volume snapshot. In such cases, snapshots will be stored in ZRS by default. Existing Backup Instances and regions without ZRS support will continue to have snapshots stored as LRS.
 - **Recovery points**: Supports up to **450** recovery points, which allows you customize **daily** or **weekly** schedules to align your backup strategy with business continuity and compliance needs.
 - **Backup tier**: Supports operational tier.