What have we learned from past projects?
Maintenance of machines (with state) expensive
- ~5X to 10X cost of HW/SW
- Stateless machines can be trivial to maintain (Hotmail)
System admin keeps system available; 1/3 to 1/2 of Cost of Ownership?
- System + clever human working during failure = uptime (failure often occurs during upgrades, reconfiguration)
- Also growth plans, user training, fix performance bugs
Know how evaluate (performance and cost)
- Run system against workload, measure, innovate, repeat
- Benchmarks standardize workloads, lead to competition, evaluate alternatives; turns debates into numbers
What are 21st century research challenges? Says who?