1. A method comprising: for each device of a plurality of devices in a storage system, calculating a respective busyness value; receiving a read request that targets a particular item for which copies of the particular item are stored on at least two devices of the plurality of devices but not all of the plurality of devices; in response to receiving the read request, performing the steps of: identifying the at least two devices that store copies of the particular item; determining which particular device, of the at least two devices, has a respective busyness value that indicates that the particular device is less busy than the other devices of the at least two devices; and sending the read request to the particular device, of the at least two devices, that has a respective busyness value that indicates that the particular device is less busy than the other devices of the at least two devices; wherein: the method is performed by one or more computing devices; the respective busyness value of said each device is based, at least in part, on an interval associated with said each device; and the interval associated with said each device is based on an amount of load experienced by other devices of the plurality of devices between two consecutive read requests that are sent to each said device.