Systems and methods dynamically manage replicas of data sets. A collection of data stores is used to redundantly store one or more replicas of one or more data sets. The replicas may be used to respond to read requests from multiple sources. Upon identification of a need to allocate storage space to a data object, space used by one or more of the replicas is allocated to the data object. Various parameters may be utilized in the selection of one or more replicas whose storage space can be allocated to the data object. The parameters may be based at least in part on characteristics of the one or more data sets relative to one another.