Entropy: a consolidation manager for clusters. Fabien Hermenier, Xavier Lorca, Jean-Marc Menaud, Gilles Muller, and Julia Lawall. 21th Proceedings of the 2009 ACM SIGPLAN/SIGOPS international conference on Virtual execution environments (VEE '09). ACM, New York, NY, USA, pages 41-50.

1. Entropy: a Consolidation Manager for Clusters
Fabien Hermenier1 Xavier Lorca2 Jean-Marc Menaud1 Gilles Muller3
Julia Lawall4
1 ASCOLA group, ´E
cole des Mines de Nantes
2 Constraints group, ´E
cole des Mines de Nantes
3 INRIA-R´egal, ´E
cole des Mines de Nantes
4 DIKU, University of Copenhagen
International Conference on Virtual Execution Environments,
Washington D.C., March 12 2009

2. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Context
Cluster environment
Static allocation of the resources to jobs
Resources are underused
Static allocation of CPUs vs. dynamic utilization
Dynamic Consolidation
Each task of a job is embedded into a Virtual Machine (VM)
Resources are allocated depending on tasks needs
VMs are packed to be hosted on a reduced number of nodes
VMs are re-packed when necessary with migrations
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Entropy: a Consolidation Manager for Clusters

3. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Challenge
Issues
Packing the VMs may require several migrations
Some migrations have to be delayed to succeed.
Temporary hosting may be necessary
! Migrations take time
! Performance degrades
Reactivity is essential
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Entropy: a Consolidation Manager for Clusters

4. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Our proposal
Entropy
A dynamic consolidation manager for clusters,
Plans the migration process
Reduces the duration of the migration process to improve reactivity
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Entropy: a Consolidation Manager for Clusters

5. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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6. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Global Design of Entropy
A Configuration :
Each VM is assigned on a node,
Each VM requires a fixed amount of memory.
VMs executing a computation are active and require a private CPU.
May be viable
Example
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7. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Global Design of Entropy
Monitor
Extract the current configuration :
The position of each VMs and its CPU consumption
An indication of which of the VMs are active and inactive
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8. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Global Design of Entropy
Reconfiguration Algorithm
VMPP - Compute a viable configuration using a minimum number
of nodes
VMRP - Plan and reduce the reconfiguration process if necessary
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9. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Global Design of Entropy
Execution
Decompose a plan into simple migrations
Migrations orders are sent to the concerned VMM
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Entropy: a Consolidation Manager for Clusters

10. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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11. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Packing the Virtual Machines
Definition
The Virtual Machines Packing Problem (VMPP)
Compute the minimum number of nodes needed for a viable
configuration
Example
(a) viable but non minimal (b) viable and minimal
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12. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Packing the virtual machines
Approach
Based on constraint programming,
Each condition defining a viable configuration is a constraint.
The constraint solver :
Computes a viable configuration from the current one
Reduces the number of used nodes until the minimum or a timeout.
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Entropy: a Consolidation Manager for Clusters

13. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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14. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Migrations have to be ordered
Example
Current Result
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15. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Migrations have to be ordered
Example
(1) non-viable (2)
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16. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Migrations have to be ordered
Example
(1) Ok (2) Ok
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Entropy: a Consolidation Manager for Clusters

17. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Inter-dependant migrations require a pivot
Example
Current Result
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18. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Inter-dependant migrations require a pivot
Example
Current non-viable
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19. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
Inter-dependant migrations require a pivot
Example
(1) (2) (3)
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20. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Planning a reconfiguration
The Reconfiguration Plan
Describes a viable reconfiguration process
Migrations feasible in parallel are grouped into a step
Steps are executed sequentially
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21. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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22. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Reducing the reconfiguration process
VMRP - Looking for an equivalent configuration
Which is a solution of the VMPP
Where its associated plan has a minimal ”cost”
Method
The cost of a plan is estimated using a migration cost model
The VMRP computes equivalent configurations with ”cheap”
reconfiguration plans until the minimum or a timeout.
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23. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Reducing the reconfiguration process
Example
(1)
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24. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Reducing the reconfiguration process
Example
(1) (2) (3)
cost = 9
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25. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Reducing the reconfiguration process
Example
(1) (2) (3)
cost = 9
(1) (2)
cost = 4
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26. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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27. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Comparison against ”First Fit Decrease”
Timeouts to have a non-trivial solution with Entropy estimated
using random configurations :
30 secs. for the packing
35 secs. for minimizing the migrations
The packing is equivalent or better. Small
benefits for 42% of the configurations
Cost of the resulting plan reduced by at
least 90%
Cost
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28. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Experiments on a cluster
Environment
1 node hosting the consolidation manager
3 nodes for serving the VMs virtual disks
35 nodes running a hypervisor
35 VMs executing a collection of NASGrid Benchmarks
Method
All the benchmarks are launched at the same time
Comparison between
Static allocation without consolidation
Dynamic consolidation using FFD
Dynamic consolidation using Entropy
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29. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Experiments on a cluster
Benefits
Better reactivity
Stable packing
Reduced overhead
Comparing the reconfigurations against FFD
Cost : -90%
Duration : -74%
Nb of reconfigurations : x2
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30. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Experiments on a cluster
Benefits
Better reactivity
Stable packing
Reduced overhead
Impact on the packing
Smaller plans imply fewer pivots
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Entropy: a Consolidation Manager for Clusters

31. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Experiments on a cluster
Benefits
Better reactivity
Stable packing
Reduced overhead
Impact on performance
Overhead reduced by 9%
Node per hour consumption
reduced by 25%
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Entropy: a Consolidation Manager for Clusters

32. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
1 Design
2 Packing the Virtual Machines
3 Planning the migrations
4 Minimizing the migrations
5 Evaluation
6 Conclusion
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33. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Conclusion
The interest of the dynamic consolidation is limited by the
duration of the reconfiguration process.
Entropy
Reducing the cost of a plan is an efficient solution to reduce its
duration
1 minute to compute a solution reduces the reconfiguration process
by up to 8 minutes.
Reduces the nodes per hour consumption by 25% as compared to
FFD and the overhead by 9%.
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34. Design Packing the Virtual Machines Planning the migrations Minimizing the migrations Evaluation Conclusion
Questions ?
http ://entropy.gforge.inria.fr
Binary and sources available on LGPL
Uses the Xen Hypervisor and the ganglia monitoring system
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