US Patent 12061812 Unmapping logical block addresses of remote asynchronously replicated volumes

Unmap extents transmitted in delta sets are used to unmap LBAs on remote replicas of asynchronously replicated storage objects. A host server sends a SCSI unmap command to a production storage array to unmap a range of logical block addresses. In response, the production storage array creates an unmap extent that identifies the local and remote replicas, starting LBA, and number of LBAs to be unmapped. At the end of each asynchronous replication cycle, unmap extents and updated data are sent to a disaster recovery storage array in a delta set that preserves chronological ordering. The disaster recovery storage array receives the delta set and discards cached data corresponding to the unmapped LBAs indicated in the unmap extents and de-allocates the backend storage space. Integrating unmap extents with updated data in delta sets maintains point-in-time consistency and is more efficient than sending zero data.