elastictree : saving energy in data center networks
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ElasticTree : Saving Energy in Data Center Networks . 許倫愷 2013/5/28. About the paper. Brandon Heller , Srini Seetharaman , Priya Mahadevan , Yiannis Yiakoumis , Puneet Sharma , Sujata Banerjee , Nick McKeown NSDI’10 ( USENIX conference on Networked systems design and implementation ) - PowerPoint PPT PresentationTRANSCRIPT
ElasticTree: Saving Energy in Data Center Networks 許倫愷2013/5/28
About the paperBrandon Heller, Srini Seetharaman, Priya Mahadevan, Yiannis Yiakoumis, Puneet Sharma, Sujata Banerjee, Nick McKeownNSDI’10 (USENIX conference on Networked systems design and implementation)Citation: 17416 pages
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
The motivation
The motivation
Very inefficient!!
Desired
Why wasting powerProvisioning for peak Time varying traffic demands Low efficiency at low loads
The goal of ElasticTree
The approach…Turn off unneeded links and switches
The challengePerformanceFault toleranceScalability
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
IntroductionWhat is ElasticTree:
ElasticTree is a system for dynamically adapting the energy consumption of a data center network
• What does it do:
Finding minimum-power network subsets across a range of traffic patternsTrade-off:
energy efficiency, performance and robustness
Introduction
Data center network(Traditional) 2N Tree:
One failure can cut the effective bisection bandwidth in half; two failures can disconnect servers
Data center networkFat tree: SIGCOMM 2008, A Scalable, Commodity Data Center Network Architecture
Data center networkprovision for peak workload Traffic varies daily, weekly, monthly, and yearly.
Energy Proportionality The strategy: turn off the links and switches that we don’t need
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
ElasticTreeElasticTree is a system for dynamically adapting the energy consumption of a data center network
ElasticTreeIf 0.2 Gbps of traffic per host ,1 Gbps link…
ElasticTree13/20 switches and 28/48 links stay active ElasticTree reduces network power by 38%
0.2
0.4
0.8
ElasticTreeThe optimizer: find the minimum- power network subset which satisfies current traffic conditions
OptimizerAs traffic conditions change, the optimizer continuously re-computes the optimal network subset 3 approaches:Formal Model , Greedy Bin-Packing , Topology-aware Heuristic
Optimizer comparison
Formal modelFinding the optimal flow assignment alone is an NP-complete problem for integer flows.Derived from standard multi-commodity flow (MCF) problem The model outputs a subset of the original topology, plus the routes taken by each flow to satisfy the traffic matrix O(n^3.5+)
Greedy Bin-PackingStrategy: choose the leftmost one with sufficient capacity O(n^2+)
1G link
Greedy Bin-Packing1G link
Topo-aware Heuristic1. does not compute the set of flow routes 2. assumes perfectly divisible flows => pack every link to full utilization and reduce TCP bandwidth => starter subset Decoupling power optimization from routing : => can be applied alongside any fat tree routing algorithm
Topo-aware HeuristicAn edge switch doesn’t care which aggregation switches are active, but instead, how many are active
Topo-aware HeuristicDecoupling power optimization from routing
Optimizer comparison
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
How to testK = 6, fat tree
OpenFlow
AnalysisTraffic pattern:
Near: servers communicate only with other servers through their edge switch Far: servers communicate only with servers in other pods
AnalysisRandom demand:
Individual aggregation/core switches turning on/off
Analysis 70% to outside, 30% inside DCN
Different traffic load
Analysis: redundancyIf only the MST is on => no redundancy => no fault tolerance
Analysis: redundancy+MST: additive cost, multiplicative benefit
Analysis: latency
0.25 0.33 0.5
Need safety margin!!
Ethernet overheads (preamble, inter-frame spacing, and the CRC) cause the egress buffer to fill up Packets either get dropped or significantly delayed
Analysis: latencySafety margin is the amount of capacity reserved at every link by the optimizer Traffic overload is the amount each host sends and receives beyond the original traffic matrix
Trade-off between Energy and Performance
OutlineThe big pictureIntroductionElasticTree systemAnalysisConclusion
Summary
Reference The paperThe slide (by the author)A youtube video (by the author, too)http://www.youtube.com/watch?v=G2_D-CH4tQk
Questions
Thank you!