In a write by-peer-reference, a storage device client writes a data block to a target storage device in the storage system by sending a write request to the target storage device, the write request specifying information used to obtain the data block from a source storage device in the storage system. The target storage device sends a read request to the source storage device for the data block. The source storage device sends the data block to the target storage device, which then writes the data block to the target storage device. The data block is thus written to the target storage device without the storage device client transmitting the data block itself to the target storage device.