The article is devoted to the analysis of the efficiency of the system of dynamic block access to data of ultra-large distributed ERS archives, implemented according to the technology developed at the Space Research Institute. The system under consideration is intended to prepare the required set of data blocks with given characteristics for their processing on a server cluster. Based on the analysis of the most significant factors affecting the performance of this system, a methodology was developed that makes it possible to estimate the preparation time of the required data set using the existing hardware infrastructure.