NA65 experiment at CERN SPS will measure an inclusive differential cross-section of $D_s$ production in proton-nucleus interactions with a consecutive decay to $\tau$. The study will allow a better evaluation of $\nu_{\tau}$ flux in neutrino experiments, as this process is a main source of $\nu_{\tau}$ in the beams. The experimental method is based on a use of high resolution emulsion detectors for effective registration of short lived particles and use of powerful automatic tools for the readout of information from the emulsion. Main data sample will be collected in 2021-22. Data analysis is a challenge from point of view of high track density ($\sim10^5/cm^2$) and amount of data to be processed. A status of the pilot run data analysis and prospects of mass data processing, which requires resources of big data storage and distributed parallelization of computationally intensive tasks, is presented.