We present new fast numerical simulations of cosmic microwave background and large scale structure in the case in which the cosmological dark matter is made entirely or partly made of mirror matter .
We consider scalar adiabatic primordial perturbations at linear scales in a flat Universe .
The speed of the simulations allows us for the first time to use Markov Chain Monte Carlo analyses to constrain the mirror parameters .
A Universe with pure mirror matter can fit very well the observations , equivalently to the case of an admixture with cold dark matter .
In both cases , the cosmological models estimate the presence of a consistent amount of mirror dark matter , 0.06 \lesssim \Omega _ { mirror } h ^ { 2 } \lesssim 0.12 .