Inventive systems, techniques, and program products for copy-on-read, particularly in the context of disaster recovery (DR), are described. The inventive concepts include: a primary system for copy-on-read processing and disaster recovery, the primary system comprising: a primary storage volume available at a primary system, the primary storage volume storing one or more data portions; a record of regions of the primary storage volume, wherein a given region of the primary storage volume is marked when a given data portion stored on the primary storage volume is sent to a disaster recovery system; and a record monitoring component configured to determine whether one or more later writes to marked region(s) of the primary storage volume should be immediately replicated to the disaster recovery system, wherein the later writes occur after replicating the given data portion stored on the primary storage volume to the disaster recovery system.