9. Your next interview is at one of the FAANG companies. Your friend who works there, has in her free time, built a new distributed file system called "FAANGFS", which uses full file serving+caching like AFS but instead of AFS' "callback promise", FAANGFS instead uses NFS' client caching (with timestamps) for the whole file the latter is intended to allow two or more clients to simultaneously access a file. a. Give a key advantage and key disadvantage of this design decision of FAANGFS. b. FAANGFS uses prefetching - when a client requests a file F in a directory D, the client proactively fetches not just the entire file F, but also all the files in directory D (but not in recursive sub-directories of D). Give a key advantage and a key disadvantage of this prefetching design decision. c. In its client caching variant, instead of using the NSF rule for validity of the file (each time it is accessed): (Old NFS rule) A cache entry at time T is valid if either: 1) (T-Tc < t) or 2) if #1 is false, then (Tm client = Tm server) FAANGFS instead uses (here t is freshness interval): (New FAANGFS rule) A cache entry at time T is valid if either: 1) (Tm client Tm server) or 2) if #1 is false, then (T-Tc < t). = Is this change a good idea? If yes, say why. If no, say why not. 5