Cloud Computing - Department of Computer Science

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Nov 3, 2013 (3 years and 8 months ago)

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CLOUD COMPUTING

AN OVERVIEW &

QUALITY OF SERVICE


Hamzeh Khazaei



University of Manitoba

Department of Computer Science

Jan 28, 2010

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Cloud Computing
-

Definition


There is no unique and standard definition out there


However, it is generally accepted that CC refers to
a new IT paradigm for users


One of those definitions:


Cloud computing is a style of computing paradigm in
which typically real
-
time scalable resources such as
files, data, software, hardware, and third party
services can be accessible from a Web browser via the
Internet to users


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Cloud computing
-

Characteristics


Agility


On demand computing infrastructure


Linearly scalable


challenge


Reliability and fault tolerance


Self healing


Hot backups, etc


SLA driven


Policies on how quickly requests are processed


Multi
-
tenancy


Several customers share infrastructure, without compromising
privacy and security of each of the customer’s data


Service
-
oriented


compose applications out of loosely coupled services. One
service failure will not disrupt other services. Expose these services as API’s


Virtualized


decoupled from underlying hardware. Multiple applications can run in
one computer


Data, Data, Data


Distributing, partitioning, security, and synchronization

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Computing Paradigm Shift

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Cloud Computing
-

Some terms


Term cloud is used as a metaphor for internet


Concept generally incorporates combinations of the following


Infrastructure as a service (
IaaS
)


Platform as a service (
PaaS
)


Software as a service(
SaaS
)


Not to be confused with


Grid Computing


a form of distributed computing


Cluster of loosely coupled, networked computers acting in concert to perform
very large tasks


Utility Computing


packaging of computing resources such as computing
power, storage, also a metered services


Autonomic computing


self managed




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Cloud Computing Model

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Cloud Computing Framework

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Cloud Computing Architecture

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Commercial clouds


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Public, Private and Hybrid clouds

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Quality of Service


Everything in cloud computing is delivered as service


So quality of service is inevitable


QoS has multiple aspects such as:


Response time


Throughput


Availability


Reliability


Security



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Service Level Agreement, SLA



The SLA is a contract negotiated and agreed between
a customer and a service provider


Service provider is required to execute service requests
from a customer within negotiated quality of service
requirements for a given price


Due to variable load, dynamically provisioning
computing resources to meet an SLA and allow for an
optimum resource utilization will not be an easy task

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QoS requirements for a Cloud
-

ideal


The QoS must system be able to manage several
simultaneous services with a specific response time
limitation for each service


The QoS system must supply service differentiation in
the service provider to the consumer


consumer
category


The QoS system must support the grouping of
interactions in sessions.


The QoS system should not require modification in the
system software of the servers


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QoS requirements for a Cloud
-

ideal


The QoS system should be easy to configure


The QoS system must be scalable to operate in both
a single server and a cluster of servers


The QoS system must provide protection against
overloads and low utilization


The QoS system
may

support dynamic negotiation
of parameters

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High Level Architecture of QoS

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Service Performance and Analysis in Cloud Computing


For the commercial success of cloud computing the
ability to deliver QoS guaranteed services is crucial


Clearly customers are more concerned about response
time rather than other performance metrics


Usually customers are more inclined to the percentile of
time in which they receive their services less than a
given value


P
-
percentile
: it means a given customer receives p% of
his services less than a pre
-
defined time value in the
SLA


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Some Important Questions regarding
Service Performance:

1.
For a given arrival rate of requests and given service
rate what level of QoS can be guaranteed?

2.
What is the minimal service rate for a given percentile
of the response time and a given service arrival rate?

3.
How many number of customers can be supported so
that a given percentile of the response time can be
still guaranteed when service rate is given?

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An Example Queuing Model

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Cluster, Grid and Cloud: Google trend

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Thank You !!!


Any Question?