Lecture 4 power provisioning
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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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Lecture 4 power provisioning

Lecture 4: Power Provisioning

Prof. Fred Chong

290N Green Computing


Power provisioning

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


Power distribution revisited

Power Distribution Revisited


Measured load vs power

Measured Load vs Power


Modeled vs measured pdu power

Modeled vs. Measured PDU Power


Methodology

Methodology


Workloads

Workloads

  • Websearch – high request throughput and large data size

  • Webmail – high I/O

  • Mapreduce – large offline batch jobs


Websearch results

Websearch Results


Webmail results

Webmail Results


Mapreduce results

Mapreduce Results


Mixed load

Mixed Load


Real datacenter

Real Datacenter


Time at power level

Time at Power Level

80 servers

800 servers

8000 servers


Oversubscription opportunity

Oversubscription Opportunity

  • 7% for racks (80)

  • 22% for PDUs (800)

  • 28% for clusters (8000)

    • Could have hosted almost 40% more machines


Power capping

Power Capping


Observed power

Observed Power


Cpu dvs

CPU DVS


Idle power

Idle Power


Energy savings

Energy Savings


Underdeployment

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


Modeling costs

Modeling Costs

TCO =datacenter depreciation + datacenter opex +server depreciation + server opex


Per critical watt

$ per critical watt


Case a

Case A

  • Dell 2950 III EnergySmart

    • 16GB of RAM and 4 disks

    • 300 Watts

    • $6K


Assumptions

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.


Cost breakdown a

Cost Breakdown A


Case b

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.


Cost breakdown b

Cost Breakdown B


Utilization

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


Power provisioning problems

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)


Case b with 50 occupancy

Case B with 50% Occupancy


Partial utilization costs

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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