Efficient space allocation in gathered-write backend change volumes

A computer program product for replicating data from a primary site to a secondary site, the computer program product comprising a non-transitory computer-readable storage medium having computer-usable program code embodied therein, the computer-usable program code configured to perform the following when executed by at least one processor:

• track, by a primary storage system at a primary site, updates to storage elements of a primary volume over a specified period of time;
• capture the updates in a change volume located on the primary storage system;
• calculate, by the primary storage system, a size associated with the updates;
• communicate, by the primary storage system, the size to a secondary storage system at a secondary site;
• adjust, by the secondary storage system, the size to account for data-size reduction that occurs on the secondary storage system;
• and
• allocate, by the secondary storage system within a secondary volume, an amount of storage space needed to accommodate the updates in view of the adjusted size and then replicate the updates from the change volume to the secondary volume.

A system for replicating data from a primary site to a secondary site, the system comprising:

• at least one processor;
• at least one memory device operably coupled to the at least one processor and storing instructions for execution on the at least one processor, the instructions causing the at least one processor to:
• track, by a primary storage system at a primary site, updates to storage elements of a primary volume over a specified period of time;
• capturing the updates in a change volume located on the primary storage system;
• calculate, by the primary storage system, a size associated with the updates;
• communicate, by the primary storage system, the size to a secondary storage system at a secondary site;
• adjust, by the secondary storage system, the size to account for data-size reduction that occurs on the secondary storage system;
• and
• allocate, by the secondary storage system within a secondary volume, an amount of storage space needed to accommodate the updates in view of the adjusted size and then replicate the updates from the change volume to the secondary volume.