Energy Aware Network Operations
Authors: Priya Mahadevan, Puneet Sharma, Sujata Banerjee, Parthasarathy Ranganathan
HP LabsIEEE Global Internet Symposium (April 2009)
Speaker: Sookhyun Yang
Introduction
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• This paper analyzes three energy-saving schemes to configure a switch in a data center network with link redundancy.
[Data center network topology]
Energy Saving in a Switch• Linear power model
– Power consumed by each switch depends on • Number of active ports • Line capacity of a port
• How can we control a switch for saving energy?– Disable a switch port– Dynamically adapt a port’s link
capacity based on its load– Turn off a line-card that have no
active ports– Power off a switch that is not
being used
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[A switch with line-cards]Line-card
port
Three Energy Saving Schemes• Centralized approach
• LSA (Link State Adaptation)– Adapts a port’s link capacity (disabled,
10Mbps, 100Mbps, and 1Gbps) according to link utilization.
• NTC (Network Traffic Consolidation)– Consolidates traffic into fewer links
(and switches).
– Disables unused links (and switches).
• SLC (Server Load Consolidation)– Migrates jobs for minimizing the
number of servers being used.
– Applies NTC schemes.
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[Data center network topology]
Variations of the Three Schemes
• SL (Service Level) Awareness– Adds a constraint to ensure that a link’s utilization never
exceeds a certain threshold.
– Ensures that at least one redundant link exists.
• SL awareness policy is combined with each of the three schemes.
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Simulation Set-up: Workload
• Simulation based on workload of observed traffic
• 292 web-servers for 5days in April 2008
• System configuration of 292 web-severs– Quad-core processors, two 1Gbps network cards
– Different RAM sizes: 193 servers have 4 GB RAM, 69 servers have 8GB RAM, and 30 servers have 16GB RAM.
• Observed results– Workload is memory-sensitive
• 130 servers use 90% or greater amount of memory, 64 servers use less than 40%.
– Both network bandwidth and CPU of all servers are utilized at most 10%.
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7[Data center network topology]
292 web servers
26 rack switches
(48 ports per switch)
Simulation Set-up: Network Topology
2 tier-2 switch(6 line card per switch,24 ports per line card)
Simulation: How to Compute Power Consumption
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Line-card with no active ports
Line speed
• Power consumption
• Perfect knowledge of an oracle – Link utilization
– Job’s traffic specification
– Network topology
LSA (Link State Adaptation)• Link characteristics from 5-day measurement
– 90% of links (light traffic) can be set 10 or 100Mbps.
– Less than 5% of links (heavy traffic) need to be set 1Gbps.
• LSA’s distribution of link speeds between rack and tier-2 switches
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LSA vs. SL-aware LSA
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Simulation Results
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LSA (Link state adaptation)
NTC (Network
traffic consolidatio
n)
SLC (Server load consolidation)
Deployment Issues
• Track traffic workload– Adapt link capacity based on link utilization statistics
– Predict incoming/outgoing traffic
• Transition time for adapting link-speeds is between 1-3 seconds, which can affect network performance.– Buffer or ensure the existence of back-up paths
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Q&AQ&A
Thank you!
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