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Lecture 4: Power Provisioning

Lecture 4: Power Provisioning. Prof. Fred Chong 290N Green Computing. Power Provisioning. $10-22 per deployed IT Watt Given 10 year depreciation cycle $1-2.20 per Watt per year Assume $0.07 per kilowatt-hr and PUE 2.0 8766 hours in a year (8766 / 1000) * $0.07 * 2.0 = $1.22724

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Lecture 4: Power Provisioning

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  1. Lecture 4: Power Provisioning Prof. Fred Chong 290N Green Computing

  2. Power Provisioning • $10-22 per deployed IT Watt • Given 10 year depreciation cycle • $1-2.20 per Watt per year • Assume $0.07 per kilowatt-hr and PUE 2.0 • 8766 hours in a year • (8766 / 1000) * $0.07 * 2.0 = $1.22724 • Up to 2X cost in provisioning • eg. 50% full datacenter = 2X provisioning cost

  3. Power Distribution Revisited

  4. Measured Load vs Power

  5. Modeled vs. Measured PDU Power

  6. Methodology

  7. Workloads • Websearch – high request throughput and large data size • Webmail – high I/O • Mapreduce – large offline batch jobs

  8. Websearch Results

  9. Webmail Results

  10. Mapreduce Results

  11. Mixed Load

  12. Real Datacenter

  13. Time at Power Level 80 servers 800 servers 8000 servers

  14. Oversubscription Opportunity • 7% for racks (80) • 22% for PDUs (800) • 28% for clusters (8000) • Could have hosted almost 40% more machines

  15. Power Capping

  16. Observed Power

  17. CPU DVS

  18. Idle Power

  19. Energy Savings

  20. Underdeployment • New facilities plan for growth • Also discretization of capacity • Eg 2.5kW circuit may have four 520W servers • 17% underutilized, but can’t have one more

  21. Modeling Costs TCO = datacenter depreciation + datacenter opex + server depreciation + server opex

  22. $ per critical watt

  23. Case A • Dell 2950 III EnergySmart • 16GB of RAM and 4 disks • 300 Watts • $6K

  24. Assumptions • The cost of electricity is the 2006 average US industrial rate ay 6.2 cents/kWh. • The interest rate a business must pay on their loans is 12%. • The cost of datacenter construction is $15/W amortized over 12 years. • Datacenter opex is $0.03/W/month. • The datacenter has a PUE of 2.0. • Server lifetime is 4 years, and server repair and maintenance is 5% of capex per year. • The server’s average power draw is 75% of peak power.

  25. Cost Breakdown A

  26. Case B • higher-powered server • 500W • $2K • energy cost of $0.10/kWh • datacenter related costs rise to 46% of the total • energy costs to 25% • server costs falling to 31%. • hosting cost of such a server, i.e., the cost of all infrastructure and power to house it, is more than twice the cost of purchasing and maintaining the server.

  27. Cost Breakdown B

  28. Utilization • CPU Utilization of 50% => 75% Peak Power • Nameplate 500W server • with all options (max mem, disk, PCI cards) • but more commonly 300W • Thus 60% utilized => 1.66x OPEX • Vendor power calculator assumes 100% CPU utilization

  29. Power Provisioning Problems • Assume 30% CPU utilization and provision power accordingly • 200W instead of 300W • Variations could cause server to overhead or trip a breaker • Adding memory or disk would require physical decompaction of racks • Thus 20-50% slack space common • Eg 10MW provisioned power => 4-6 MW actual power (plus PUE overhead)

  30. Case B with 50% Occupancy

  31. Partial Utilization Costs • Partially utilized servers use less power • Appear to cost less in OPEX cost per server • But produce less value in terms of applications • Need metric for application value • Eg number of transactions, number of web searches • Divide TCO by metric • Eg TCO = $1M/month, 100M transactions/month => 1 cent / transaction • Eg TCO = $1M/month, 50M transactions/month => 2 cents / transaction (2X cost)

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