According to examples, an apparatus may include a processor and a non-transitory machine-readable storage medium comprising instructions executable by the processor to assign a first object identifier and a data identifier to a first volume, the first object identifier being assigned exclusively to the first volume. The instructions may also be executable by the processor to identify an identifier of a second volume, determined whether the identifier of the second volume matches the data identifier, and based on a determination that the identifier of the second volume matches the data identifier of the first volume, configure a replication relationship between the first volume and the second volume.