Provided are, among other things, systems, methods and techniques for controlling data synchronization. Local data-writing operations, made across a number of logical storage units on different data-storage devices, are divided into batches, the batches corresponding to different time segments. The data-writing operations, together with an indication of boundaries between the batches, are transmitted to a remote data-storage location. The boundaries between the batches are determined by at least one of: (1) identifying a period of time of sufficient duration during which no data-writing operations were performed and declaring a point during said period of time as one of the boundaries, (2) obtaining agreement from a plurality of entities, and (3) declaring the boundaries at pre-scheduled points in time.