Post on 13-May-2023
An Approach to Reduce the Energy Cost of the Arbitrary Tree
Replication Protocol
e-Energy 2010
14. April, Passau, Germany
Robert Basmadjian and Hermann de Meer
Overview Replication
Replication is used to:
Achieve fault-tolerance
Improve the system performance
Multiple replicas lead to inconsistency problems
Replica Control Protocols (RCPs) ensure synchronization
RCPs implement two operations: read and write
To ensure one-copy equivalence:
Write operation stores a new value of data
Read operation returns the most recent value written
2An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Overview Replication
Quorum systems serve as a tool to achieve one-copy equivalence:
Pair-wise non-empty intersections of quorums
Quorum-based RCPs differ according to three parameters:
Quorum size
Availability
Load
Quorum-based RCPs can be classified into:
Non-structured
Structured
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Overview Energy Efficiency
Building energy-efficient distributed systems:
Increase of energy costs (fuel)
Desire to reduce CO2 emissions
Minimizing and balancing the system’s energy consumption are as important as:
Reliability
Security
Fault tolerance
Several techniques to save energy consumption
Desirable to keep the same overall performance level
4An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Overview Motivation and Results
A model to compute the energy cost of each operation of quorum-based RCPs
An approach applied to a particular tree-structured RCP:
Cease the utilization of a significant amount of replicas
Reorganize the remaining replicas into a new logical structure
Obtained results:
Diminished overall energy consumption
Reduced energy cost of the operations
Comparable performance as the original protocol
5An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Outline
Energy Cost Model
The Arbitrary Tree Protocol
Energy Efficient Approach
Comparison
Conclusion and Perspectives
6An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Energy Cost Model
Each operation is carried out in two phases:
Sending the request to all the members of a quorum
Receiving the response from all the members of the quorum
The energy consumed is modeled by summing
The operation initiator’s component and connector
The quorum members’ components, connectors and storage media
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Energy Cost Model An Example of a Read Operation
8
Logic and
to/from
connector
Logic, to/from
component and
remote
communication
An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Client Replica
Logic, to/from
component,
remote
communication
and buffering
Logic, to/from
connector and
to/from disk
Disk access and
to/from
component
Energy Cost Model General Quorum-based Costs
Read operation:
rqSize*[(Replica’s component and connector) + (Storage access
for read) + (marshal and unmarshal) + (Remote connection) +
(Message sent) + (Message received)] + (Client’s component) +
(to/from component)
Write operation:
wqSize*[(Replica’s component and connector) + (Storage access
for write) + (marshal and unmarshal) + (Remote connection) +
(Message sent) + (Message received)] + (Client’s component) +
(to/from component)
9An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
The Arbitrary Tree Protocol
Nodes of the tree can be:
Logical
Physical (replica)
A physical level has at least one physical node
A logical level has all of its nodes logical
A read operation: any single replica of every physical level
A write operation: all replicas of a single physical level
10An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
The Arbitrary Tree Protocol An Example for 81 replicas
11An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
A logical root node
sqrt(n) = 9
4 replicas
(n – 28)/sqrt(n) – 7
26.5
n > 64
The Arbitrary Tree Protocol The Proposed Algorithm: Advantages
Read operations have a quorum size of sqrt(n), are highly available and induce a load of 0.25
Write operations have a quorum size of sqrt(n), are highly available and induce a load of 1/sqrt(n)
12An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Energy Efficient ApproachOverview
Objectives:
Keep the same protocol as the one proposed for Arbitrary Tree
Reduce the energy consumption of AT protocol
Keep a comparable performance wrt AT protocol
Achievements
Logical rearrangement of the replicas into a rectangle structure
Cease the utilization of a significant amount of replicas
Data consistency is preserved
13An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Energy Efficient ApproachRectangle Structure
Organize logically thereplicas into a rectangleof height h > 1 andwidth w > 1
Transformation:
Set the width of the rectangle to be 4
Set the height of the rectangle to be sqrt(n)
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Energy Efficient ApproachTransformation
15An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Comparison
Studies for n = 75, 100, 150 and 200 replicas
Every replica is up 70% of the time
For each operation, comparison is performed in terms of:
Quorum size (between 1 and n)
Availability (between 0 and 1)
Load (between 0 and 1)
Energy cost in terms of a single client-replica cost
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ComparisonRead Operation
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ComparisonWrite Operation
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ComparisonSaved Energy Consumption
Number of Replicas Arbitrary Tree Rectangle
n = 75 0 39
n = 100 0 60
n = 150 0 102
n = 200 0 144
19An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany
Conclusion and Perspectives
Compute the energy cost of quorum-based RCP
Approach to reduce the energy consumption of the AT protocol
Ceasing the usage of replicas
Logical transformation into a rectangle structure
Perspectives:
Expectation of energy cost in terms of load?
Read-only operations, select replicas with small PUE or good geographical regions (Iceland or Africa)
Compute the energy cost of other quorum-based RCP
20An Approach to Reduce the Energy Cost of the Arbitrary Tree Replication Protocole-Energy 2010, 14. April, Passau, Germany