[20/20/Discussion] Memory Hierarchy: Caching is heavily used in some
WSC designs to reduce latency, and there are multiple caching options to satisfy
varying access patterns and requirements.
a. [20] Let’s consider the design options for streaming rich media from the Web
(e.g., Netflix). First we need to estimate the number of videos, number of encode
formats per video, and concurrent viewing users. Assume a streaming video provider
that has 12,000 titles for online streaming, each title having at least four
encode formats (at 500, 1000, 1600, and 2200 kbps). Let’s also assume that there
are 100,000 concurrent viewers for the entire site, and an average video is 75 min
long (accounting for both 30-min shows and 2-h videos). Estimate the total
storage capacity, I/O and network bandwidths, and video-streaming-related
computation requirements.
b. [20] What are the access patterns and reference locality characteristics per user,
per video, and across all videos? (Hint: Random versus sequential, good versus
poor temporal and spatial locality, relatively small versus large working set
size.)
c. [Discussion] What movie storage options exist by using DRAM, SSD, and hard
drives? Compare them in performance and TCO. Would new memory technologies
like those in Problem 6.17(d) be useful?