In this paper , a unified dark fluid with constant adiabatic sound speed is decomposed into cold dark matter interacting with vacuum energy .
Based on Markov chain Monte Carlo method , we constrain this model by jointing the geometry and dynamical measurement .
The geometry test includes cosmic microwave background radiation from Planck , baryon acoustic oscillation , and type Ia supernovae ; the dynamic measurement is f \sigma _ { 8 } ( z ) data points which is obtained from the growth rate via redshift-space distortion , and \sigma _ { 8 } ( z ) is the root-mean-square amplitude of the density contrast \delta at the comoving 8 h ^ { -1 } Mpc scale .
The jointed constraint shows that \alpha = 0.000662 _ { -0.000662 } ^ { +0.000173 } and \sigma _ { 8 } = 0.824 _ { -0.0166 } ^ { +0.0128 } .
The CMB and matter power spectra are both similar for the case of \alpha = mean value and that of \alpha = 0 .
However , the evolutionary curves of f \sigma _ { 8 } ( z ) are different .
This means that , to some extent , the data points of the growth rate could break the degeneracy of the dark energy models .