Cloud computing an overview quality of service
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University of Manitoba Department of Computer Science. Cloud Computing An overview & Quality of Service. Jan 28, 2010. Hamzeh Khazaei. Cloud Computing - Definition. There is no unique and standard definition out there

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Cloud Computing An overview & Quality of Service

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University of Manitoba

Department of Computer Science

Cloud Computing An overview & Quality of Service

Jan 28, 2010

Hamzeh Khazaei


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


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


Computing Paradigm Shift


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


Cloud Computing Model


Cloud Computing Framework


Cloud Computing Architecture


Commercial clouds


Public, Private and Hybrid clouds


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


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


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


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


High Level Architecture of QoS


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


Some Important Questions regarding Service Performance:

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

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

  • 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?


An Example Queuing Model


Cluster, Grid and Cloud: Google trend


Thank You !!!

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