Linux.conf.au 2014 – Day 4 – Session 3

Disaster Recovery Lessons I Hoped I’d Never Have to Learn by Bdale Garbee

  • Got backups?
    • Do you keep a copy of your essential data off-site
    • If someone called you and said your house was gone: completely devastating or just a really bad day?
  • 11th June 2013
    • Got no warnings of fire, saw it one km away and then got instant evacuation order
    • Had 20m-1h to pack (unsure of time due to heat of situation)
    • Went to leave and fire was on driveway, unable to get car out.
    • Had to park car and firefighters walked them out.
  • The fire
    • Started 1pm 11th of June 2013
    • 13,000 homes evacuated
    • 94,000 acres evacuated
    • 500 fire fighters involved
    • Destroyed – 14,290 acres ( 57.8 km²) , 511 homes, 2 people
    • Let back into property on 21 June
  • Aftermath
    • House pretty destroyed
    • Normally 2000-2200 degrees, His house got to 3000 degrees plus Fahrenheit
    • Most metals melted
  • Ready to go – what would you grab?
    • Usuaul pocket contents.. mobile phone, wallet, keys
    • Photo albums and scrape books
    • Jewelry
    • Computers
  • Stuff you havn’t thought about
    • Mobile phone charger
    • Identity documents
    • Safe deposit box key
    • Account numbers and contact info
  • Hows your insurance
    • Types and levels of coverage
      • Structure
      • Contents
      • Loss of use
      • Outbuildings
      • Landscaping
    • Replacement cost vs actual cash value
    • Personal vs Business Property – Have you even taken a business tax deduction for any of these items?
    • Costed out how much it would cost to rebuild old house, got that much money to build new cost (not the same)
  • Rapidly recoving
    • Take care of human needs first
    • Find a place to live.. being homeless sucks
    • Minimise the amount of “throw away” stuff purchased ( don’t buy stuff you don’t want to keep, eg apartment-only stuff)
    • Pick one or two things to “put back to normal” ASAP
      • Mobile phone for my son
      • Big-screen TV with cable service
      • 3d printer
      • art supplies
    • Registries and wish lists
  • Cleaning up
    • Lots of metal extracted from the ashes – copper, silver
    • Found very few intact items – a Japanese doll, a few other ceramics
    • Since house taken out by embers around 2/3s of trees intact
  • Recovering Hobbies and Small Business
    • Back on the net quickly but not back in business
    • Commitment to AJ and Mike Beatie for rocket launch

A web page in seven syscalls by Tollef Fog Heen

  • “Most of us, well at least the ones of us who have CS degrees”
  • Modern Computers – Cores, Caches, 64 bit, Virtual memory
  • Massively multi-threaded – usually 1000 threads or more
  • Relative performance of CPU -> system calls -> Disk access
  • Varnish from HTTP’s point of view is a origin server not a “http cache”
  • Two processes
    • manager process – starts child, compiles config, watchdo on child and restarts if dies
    • Child process, handles all connections, handles storage
    • params shared via shared memory
  • VCL
    • Domain specific language
    • Compiled into C when loaded
    • Can escape to C from within VCL
    • Can import plugins
  • Optimisations
    • Avoid syscalls
    • Memory workspaces
    • Length-counted strings
    • Threads
    • Don’t fight the VM, use hints
    • Don’t copy data
    • LIFO schedule threads
    • Preallocate
    • Accept filters