AFS at 25 Jim Morris Carnegie Mellon Silicon Valley

Outline Initial Goals and Ideas in 1982 Who built it. How it allowed total mobility—what needed to be added? How it fit with Athena. Why did WWW beat global AFS? What concepts are/can be used elsewhere? 2

My Personal Goals for Andrew, 1982 Quality Communication through Time and Space Jacques Barzun’s Capital Spending Priorities 1Dorms: student interaction 2Library: knowledge 3Classrooms: teaching Network > Workstation –But we got distracted. –University/IBM Goal: personal computer for every student 3

My Ideas for Andrew, system is a data base –Replace class discussion. –Today’s Answer: Gmail, Google Desktop Data glut will be a problem –Today’s Answer: Google Multi-way communication Today’s Answer: Web 2.0 Write-once, never delete data base –Today’s Answer: Wiki ARPANet(!) access for students Open access, remember who reads. Just-in-time Knowledge 4

Who Did What? John Howard –manager –Mitsubishi, SUN (retired) Dave Nichols –Client AFS 1 –Xerox, Placeware, Microsoft Mike Kazar –Client AFS 2 –Transarc, FORE, Spinnaker, …, Avere Bob Sidebotham –RPC, Volumes Google Mike West –Server – IBM (deceased) Ed Zayas –Cells Mahadev Satyanarayanan –Prototype RPC –Carnegie Mellon Al Spector –Consultant –Transarc, IBM, Google 5

But the “data base” was downgraded to a file system. Nobody understood data bases. –Computer Science Blind Spot –Relational DB was daunting –I read, and forgot, Ted Nelson’s hypertext manifesto, Computer Lib/Dream Machines. We understood the UNIX and time- sharing. –Reproduce central computing model using distributed hardware. –Processors and disks distributed 6

AFS 1 (VICE) Use a local disk. –Cheapest source of storage. Use local disk only as cache. – Many shared workstations Achieve system-wide consistency on file close—very close to UNIX on a single machine. Client polls for updates!? 7

AFS 2 Sever notifies client of changes via callbacks. –Even more complicated –Much better performance Volumes –System management –Convenient back-up –Application of indirection heuristic. 8

AFS 2 Sever notifies client of changes via callbacks. –Even more complicated –Much better performance Volumes –System management –Convenient back-up –Application of indirection heuristic. 9

Athena Open Source X Window Manager UNIX-ready Utilities –Kerberos –Zephyr The X-tape 10

Why WWW beat Global AFS Kernel mods were deadly. –Forgot Window Manager Lesson Consistency was overrated. –“Read-only” Web was useful. –File close is arbitrary check-point. URL was obvious, but crucial. HTTP & Browser blindsided us. WWW was a paradigm shift. AFS was incremental. 11

Meta Lessons Incremental Adoption Essential! –UNIX > Xerox Alto “Generative” interfaces, e.g. HTTP, win. Disruption Wins –In 1992, web page was not easily interactive. –But is was better than a file list. –AJAX’s come along if you have the market volume. 12

Questions for You Why is AFS still used today? Could callback be used on the web? 13