Wednesday, October 10, 2007

CEC: Concerning Capacity

Bob Sneed

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"
  • eco-reckless
  • Inefficiencies on small hardware are MORE inefficient on big hardware, only you can waste more before it is a problem
Not a problem when: Done wrong but no one cares (performance perception can be a major factor in escalations)

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.

The whole gallery, being updated as frequently as possible.

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