Before revision:  For this case  we present upper and lower bounds on the download time . These bounds yield insight on system performance with respect to varying popularities over the stored objects. We also derive an M/G/1 queue approximation for the system, and show with simulations that it performs well in estimating the actual system performance .
After revision:  For this case we present upper and lower bounds on the download time , and an M/G/1 queue approximation for the system, and show with simulations that it performs well in estimating the actual system performance .