Techniques are provided for processing a request. When the request is to read a data unit, information regarding the closest physical block locations is returned. When the request is to write to the data unit, information regarding one or more source block locations is returned, wherein the write is applied to one or more source blocks of the data unit. When a number of requests for the data unit exceed a threshold level and at least one quality of a service policy is not being met, a copy of the one or more source blocks of the data unit is created at a location selected based on proximity to at least one client computer from which the number of requests are high.