Get a cost-effective, point-in-time backup of managed disks using incremental snapshots. Unlike current snapshots, which are billed for the full size, incremental snapshots are billed for the delta changes to disks since the last snapshot. They’re always stored on the most cost-effective storage, for example, standard HDD, irrespective of the storage type of the parent disks. Additionally, for increased reliability, they are stored on zone redundant storage (ZRS) by default in regions that support ZRS.
Incremental snapshots provide differential capability, enabling customers and independent solution vendors (ISVs) to build backup and disaster recovery solutions for Managed Disks. It allows customers to get the changes between two snapshots of the same disk, thus copying only changed data between two snapshots across regions, reducing time and cost for backup and disaster recovery. Moreover, incremental snapshots are accessible instantaneously, enabling you to read the underlying data of incremental snapshots or restore disks from them as soon as they are created.
Incremental snapshots blog post
Incremental snapshots documentation