DistOS 2014W Lecture 7

Project

We discussed moving the proposal due date back a week. We also discussed spending the class prior to that date discussing the primary papers people had chosen in order to provide preliminary feedback. Anil spent some time going through the papers from OSDI12 and discussing which ones would make good projects and why.

• Pick a primary paper.
• Find papers that cite that paper, papers it cites, etc. to collect a body of related work.
• Don't just give a history, tell a story!

Unix and Plan 9

UNIX was built as "a castrated version of Multix", which was a very complex system. Multix was, arguably, so far ahead of its time that we are only just achieving their ambitions now. Unix was much more modest, and therefore much more achievable and successful. Just enough infrastructure to avoid reinventing the wheel. Just a couple of programmers making something for their own use. Unix was not designed as product or commercial entity at all. It was licensed out because AT&T was under severe antitrust scrutiny at the time.

They wanted few, simple abstractions so they made everything a file. Berkeley promptly broke this abstraction by introducing sockets for networking. Plan 9 finally introduced networking using the right abstractions, but was too late. Arguably the reason the BSD folks didn't use the file abstraction was because of the difference in reliability. Files are generally reliable, and failures with them are catastrophic so many applications simply didn't include logic to handle such IO errors. Networks are much less reliable and applications have to be able to deal gracefully with timeouts and other errors.

Simon's Notes

• project proposal
  • We will discuss the primary papers we've chosen on Thursday, February 6th
• possible papers, remember to pick a topic you have some chance of understanding
  • OSDI 2012
    • datacenter (filesystems for doing X, heat management, etc...)
    • web stuff
    • distributed shared memory
    • distributed network I/O infrastructure
    • distributed databases (potentially)
    • anonymity systems
  • Pick a conference (usenix is pretty systems oriented, maybe Lisa), go through their papers and find something interesting
  • tell a story that connects several papers in the topic you choose

• UNIX
  • Relation to multics
    • Multics was a complex system which was bad because it was used less, slower, etc...
    • Multics was not for end users, it was designed to support "utility computing" wherein computation was a service to be charged for
  • What?
    • Just enough infrastructure to run my programs
    • It was really just supposed to be used by programmers
    • "By programmers for programmers"
    • Software and source licensed for a nominal fee
    • "Everything is a file"
    • only difference was files that you could use seek or ones you couldn't
    • simple abstractions
  • Networking
    • Berkeley folks made sockets, not files which upset the folks at Bell labs
    • Networks aren't exactly like files because they're unreliable

• Plan 9
  • major ideas
    • procfs, later adopted by linux
  • summary
    • a very elegant attempt to follow the philosophy "everything is a file"
    • trying too hard
  • opinions
    • things that have different failure modes deserve different APIs