def savePiece(pieceIndex, data)
      id = @pieceManager.writeBlock pieceIndex, 0, data
      @pieceManagerRequests[id] = PieceManagerRequestMetadata.new(:write, pieceIndex)
      id
    end
def savePiece(pieceIndex, data)
      id = @pieceManager.writeBlock pieceIndex, 0, data
      @pieceManagerRequests[id] = PieceManagerRequestMetadata.new(:write, pieceIndex)
      id
    end
Save the specified piece to disk asynchronously.