CLOUD COMPUTING AN OVERVIEW & QUALITY OF SERVICE Hamzeh Khazaei University of Manitoba Department of Computer Science Jan 28, 2010

2 /20 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

3 /20 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

4 /20 Computing Paradigm Shift

5 /20 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

6 /20 Cloud Computing Model

7 /20 Cloud Computing Framework

8 /20 Cloud Computing Architecture

9 /20 Commercial clouds

10 /20 Public, Private and Hybrid clouds

11 /20 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

12 /20 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

13 /20 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

14 /20 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

15 /20 High Level Architecture of QoS

16 /20 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

17 /20 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?

18 /20 An Example Queuing Model

19 /20 Cluster, Grid and Cloud: Google trend

20 /20 Thank You !!! Any Question?