Cache Management for Video Servers by the Combined Use of DRAM and SSD

The combination of cost and performance offered by solid-state disks (SSDs) makes them potentially suitable for caching in video servers. However, it is necessary to determine which video segments should be cached on SSD, and how to combine DRAM and SSD caching. We introduce a dynamic programming algorithm that allows for segment popularity in determining which videos will have their initial segments (prefixes) stored on SSD, and another algorithm that determines the intervals between pairs of consecutive requests for segments, and hence which segments should be stored on DRAM. Simulations of combined caching show that prefix caching saves appreciable disk bandwidth between 17% and 60%, and that DRAM and SSD caching can be combined effectively.