1. A method for managing data, the method comprising: receiving, by a management unit coupled to a write-back cache, a request from an adapter to write a new version of a data set to a certain cache data allocation unit of the write-back cache unit, wherein the write-back cache is situated separate from the management unit, the certain cache data allocation unit comprising a current version of the data set, and wherein the new version of the data set is received from the adapter; analyzing, by the management unit based on receiving the request to write the new version of the data set, a data storage policy, the data storage policy indicating at least when the current version of the data set is to be overwritten and when the current version of the data set is to be destaged; destaging, based on the data storage policy that has been analyzed, the current version of the data set from the certain cache data allocation unit to a first storage unit; and writing, by the management unit based on the destaging, the new version of the data set received from the adapter to the certain cache allocation unit.