A method for managing a group of targets is provided. The method includes: receiving a request to update a x'th generation copy of a data entity, where x is a positive integer. Then applying an update function responsive to x such as to update a first sub-group of targets. Then receiving a request to read a y'th generation copy of the data entity and (iv) applying a retrieve function responsive to y such as to search for the y'th generation copy of the data entity in a second sub-group of targets. The first and second sub-groups intersect only once and only if y does not exceed x.