CEC: Concerning Capacity
By yakshaving on Oct 10, 2007
Bob is a fount of knowledge, I highly recommend any course/session/conversation with him. Unfortunately we are trying to pack what could be days of discussion into a tiny fraction of the time.
Bob was wondering if anyone had an LG phone charger, his is dead.
Why capacity: reduce capacity escalations, raise awareness
What is capacity: Submarine 100% underwater vs. at crush depth (the physical metaphor is what people understand) CPU 100% vs. unacceptable application performance.
Look for the Business problem not some easily observed numbers from the system (CPU, IOPS)
Capacity done wrong: over-provisioning
- HW is cheap, why not buy more (power, cooling)
- good if you sell computers
- better safe than sorry (problems pointed at insufficient HW(why didn't you buy more, it is cheap)
Bad QoS management in Small Iron == Bad QoS management on Big Iron
- Over provisioning reduces the incentive to "do it right"
- Inefficiencies on small hardware are MORE inefficient on big hardware, only you can waste more before it is a problem
Utilization has no "quality" dimension it is a measurement of busy. Utilization does not reflect the performance of useful work.
See Adrian's blog or paper (search on) "utilization is a virtually useless metric"
Without Business Metrics all you have are a bunch of numbers.