A REVIEW ON CLOUD COMPUTING

Transcription

1 A REVIEW ON CLOUD COMPUTING Battina Dinesh #1, B.Veera Mallu* 2 # Final Year B.Tech, Dept. of CSE, K L University, Vaddeswaram, AP, India *Associate Professor, Dept. of CSE, K L University, Vaddeswaram, AP, India Abstract Cloud computing describes computation, software, data access, and storage services that do not require end-user knowledge of the physical location and configuration of the system that delivers the services.cloud computing is a natural evolution of the widespread adoption of virtualization, service, autonomic and utility computing. Details are abstracted from end-users, who no longer have need for expertise in, or control over, the technology infrastructure "in the cloud" that supports them.cloud computing describes a new supplement, consumption, and delivery model for IT services based on Internet protocols, and it typically involves provisioning of dynamically scalable and often virtualized resources.it is a byproduct and consequence of the ease-of-access to remote computing sites provided by the Internet. This frequently takes the form of web-based tools or applications that users can access and use through a web browser as if it were a program installed locally on their own computer Keywords Client, Application, Platform, Infrastructure,Server. I. INTRODUCTION Cloud computing is a pay-per-use model for enabling available, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model promotes availability and is comprised of five key characteristics, three delivery models, and four deployment models. The National Institute of Standards and Technology (NIST) provide a somewhat more objective and specific definition: "Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. The term "cloud" is used as a metaphor for the Internet, based on the cloud drawing used in the past to represent the telephone network, and later to depict the Internet in computer network diagrams as an abstraction of the underlying infrastructure it represents. Most cloud computing Infrastructures consist of services delivered through common centers and built on servers. Clouds often appear as single points of access for consumers' computing needs. Commercial offerings are generally expected to meet quality of service (QoS) requirements of customers, and typically include service level agreements (SLAs) II. COMPARISONS Cloud computing derives characteristics from, but should not be confused with: 1. Autonomic computing computer systems capable of self-management 2. Client server model client server computing refers broadly to any distributed application that distinguishes between service providers (servers) and service requesters (clients). 3. Grid computing "a form of distributed computing and parallel computing, whereby a 'super and virtual computer' is composed of a cluster of networked, loosely coupled computers acting in concert to perform very large tasks" 4. Mainframe computer powerful computers used mainly by large organizations for critical applications, typically bulk data-processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing 5. Utility computing the "packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility, such as electricity" 6. Peer-to-peer distributed architecture without the need for central coordination, with participants being at the same time both suppliers and consumers of resources (in contrast to the traditional client server model) 7. Service-oriented computing Cloud computing provides services related to computing while, in a reciprocal manner, service-oriented computing consists of the computing techniques that operate on software-as-a-service. III. CHARACTERISTICS The key characteristic of cloud computing is that the computing is "in the cloud" i.e. the processing (and the related data) is not in a specified, known or static place(s). This is in contrast to a model in which the processing takes ISSN: Page 803

2 place in one or more specific servers that are known. All the other concepts mentioned are supplementary or complementary to this concept. A.KEY CHARACTERSTICS: On-demand self-service : A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed without requiring human interaction with each service s provider. Ubiquitous network access: Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, laptops, and PDAs). Location independent resource pooling : The provider s computing resources are pooled to serve all consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. The customer generally has no control or knowledge over the exact location of the provided resources. Examples of resources include storage, processing, memory, network bandwidth, and virtual machines. Rapid elasticity: Capabilities can be rapidly and elastically provisioned to quickly scale up and rapidly released to quickly scale down. To the consumer, the capabilities available for rent often appear to be infinite and can be purchased in any quantity at any time. Pay per use: Capabilities are charged using a metered, fee-forservice, or advertising based billing model to promote optimization of resource use. Examples are measuring the storage, bandwidth, and computing resources consumed and charging for the number of active user accounts per month. Clouds within an organization accrue cost between business units and may or may not use actual currency. Agility improves with users' ability to rapidly and inexpensively re-provision technological infrastructure resources. Application Programming Interface (API) accessibility to software that enables machines to interact with cloud software in the same way the user interface facilitates interaction between humans and computers. Cloud Computing systems typically use REST-based APIs. Cost is claimed to be greatly reduced and in a public cloud delivery model capital expenditure is converted to operational expenditure. This ostensibly lowers barriers to entry, as infrastructure is typically provided by a third-party and does not need to be purchased for one-time or infrequent intensive computing tasks. Pricing on a utility computing basis is finegrained with usage-based options and fewer IT skills are required for implementation (in-house). Device and location independence enable users to access systems using a web browser regardless of their location or what device they are using (e.g., PC, mobile). As infrastructure is off-site (typically provided by a third-party) and accessed via the Internet, users can connect from anywhere. Multi-tenancy enables sharing of resources and costs across a large pool of users thus allowing for Centralization of infrastructure in locations with lower costs (such as real estate, electricity, etc.). Peak-load capacity increases (users need not engineer for highest possible load-levels). Reliability is improved if multiple redundant sites are used, which makes well designed cloud computing suitable for business continuity and disaster recovery. Nonetheless, many major cloud computing services have suffered outages, and IT and business managers can at times do little when they are affected. Scalability via dynamic ("on-demand") provisioning of resources on a fine-grained, self-service basis near real-time, without users having to engineer for peak loads. Performance is monitored, and consistent and loosely coupled architectures are constructed using web services as the system interface. Security could improve due to centralization of data, increased security-focused resources, etc., but concerns can persist about loss of control over certain sensitive data, and the lack of security for stored kernels. Security is often as good as or better than under traditional systems, in part because providers are able to devote resources to solving security issues that many customers cannot afford. Providers typically log accesses, but accessing the audit logs themselves can be difficult or impossible. Furthermore, the complexity of security is greatly increased when data is distributed over a wider area and / or number of devices. Maintenance of cloud computing applications is easier, since they don't have to be installed on each user's computer. They are easier to support and to improve since the changes reach the clients instantly. Metering means that cloud computing resources usage should be measurable and should be metered per client and application on a daily, weekly, monthly, and yearly basis. ISSN: Page 804

3 IV. ARCHITECTURE A. Client: A cloud client consists of computer hardware and/or computer software that relies on cloud computing for application delivery, or that is specifically designed for delivery of cloud services and that, in either case, is essentially useless without it. Examples include some computers, phones and other devices, operating systems and browsers. B. Application: Cloud application services or "Software as a Service (SaaS)" deliver software as a service over the Internet, eliminating the need to install and run the application on the customer's own computers and simplifying maintenance and support. People tend to use the terms SaaS and cloud interchangeably, when in fact they are two different things. 1) Cloud architecture, the systems architecture of the software systems involved in the delivery of cloud computing, typically involves multiple cloud components communicating with each other over application programming interfaces, usually web services and 3-tier architecture. This resembles the UNIX philosophy of having multiple programs each doing one thing well and working together over universal interfaces. Complexity is controlled and the resulting systems are more manageable than their monolithic counterparts. The two most significant components of cloud computing architecture are known as the front end and the back end. The front end is the part seen by the client, i.e. the computer user. V. LAYERS The Internet functions through a series of network protocols that form a stack of layers, as shown in the figure (or as described in more detail in the OSI model). Once an Internet Protocol connection is established among several computers, it is possible to share services within any one of the following layers. C. Platform: Cloud platform services or "Platform as a Service (PaaS)" deliver a computing platform and/or solution stack as a service, often consuming cloud infrastructure and sustaining cloud applications. It facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers D. Infrastructure: Cloud infrastructure services, also known as "Infrastructure as a Service (IaaS)", delivers computer infrastructure - typically a platform virtualization environment - as a service. Rather than purchasing servers, software, data-center space or network equipment, clients instead buy those resources as a fully outsourced service. Suppliers typically bill such services on a utility computing basis and amount of resources consumed (and therefore the cost) will typically reflect the level of activity. IaaS evolved from virtual private server offerings. E. Server: The server s layer consists of computer hardware and/or computer software products that are specifically designed for the delivery of cloud services, including multi-core processors, cloud-specific operating systems and combined offerings. VI. DELIVERY MODELS: Cloud Software as a Service (SaaS): The capability provided to the consumer is to use the provider s applications running on a cloud infrastructure and accessible from various client devices through a thin client interface such as a Web browser (e.g., web-based ). The consumer does not manage or control the underlying cloud infrastructure, network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited userspecific application configuration settings. ISSN: Page 805

4 Cloud Platform as a Service (PaaS): The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created applications using programming languages and tools supported by the provider (e.g., java, python,.net). The consumer does not manage or control the underlying cloud infrastructure, network, servers, operating systems, or storage, but the consumer has control over the deployed applications and possibly application hosting environment configurations. Cloud Infrastructure as a Service (IaaS): The capability provided to the consumer is to rent processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly select networking components (e.g., firewalls, load balancers). A. Public Cloud: VII. DEPLOYMENT MODELS Public cloud or external cloud describes cloud computing in the traditional mainstream sense, whereby resources are dynamically provisioned on a fine-grained, selfservice basis over the Internet, via web applications/web services, from an off-site third-party provider who bills on a fine-grained utility computing basis. The cloud infrastructure is owned by an organization selling cloud services to the general public or to a large industry group. B. Community cloud: A community cloud may be established where several organizations have similar requirements and seek to share infrastructure so as to realize some of the benefits of cloud computing. With the costs spread over fewer users than a public cloud (but more than a single tenant) this option is more expensive but may offer a higher level of privacy, security and/or policy compliance. Examples of community cloud include Google's "Gov Cloud". The cloud infrastructure is Shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). C. Hybrid cloud: There is some confusion over the term "hybrid" when applied to the cloud - a standard definition of the term "Hybrid Cloud" has not yet emerged. The term "hybrid cloud" has been used to mean either two separate clouds joined together (public, private, internal or external), or a combination of virtualized cloud server instances used together with real physical hardware. The most correct definition of the term "hybrid cloud" is probably the use of physical hardware and virtualized cloud server instances together to provide a single common service. Two clouds that have been joined together are more correctly called a "combined cloud". D. Private cloud: Douglas Parkhill first described the concept of a "private computer utility" in his 1966 book The Challenge of the Computer Utility. The idea was based upon direct comparison with other industries (e.g. the electricity industry) and the extensive use of hybrid supply models to balance and mitigate risks. Private cloud and internal cloud have been described as neologisms, however the concepts themselves pre-date the term cloud by 40 years. Even within modern utility industries, hybrid models still exist despite the formation of reasonably well-functioning markets and the ability to combine multiple providers. Some vendors have used the terms to describe offerings that emulate cloud computing on private networks. These (typically virtualization automation) products offer the ability to host applications or virtual machines in a company's own set of hosts. VIII. CLASSIFICATION OF CLOUD ON THE BASIS OF SERVICE PROVIDED: Infrastructure as a service(iaas): Hardware related services are provided using the principles of Cloud Computing. These include disk storage and virtual servers. Amazon EC2, Amazon S3, Rackspace Cloud Servers are some of the leading vendors. Platform as a service(paas): Development platforms are provided on the cloud. The platforms may not be compatible with each other. Platform as a service (PaaS) the delivery of a computing platform and solution stack as a service.paas offerings facilitate deployment of applications without the cost and complexity of buying and managing the underlying hardware and software and provisioning hosting capabilities, providing all of the facilities required to support the complete life cycle of building and delivering web applications and services entirely available from the Internet.PaaS offerings may include facilities for application design, application development, testing, deployment and hosting as well as ISSN: Page 806

5 application services such as team collaboration, web service integration and marshalling, database integration, security, scalability, storage, persistence, state management, application versioning, application instrumentation and developer community facilitation. These services may be provisioned as an integrated solution over the web.google App Engine, Microsoft Azure and Saleforce s force.com are the leaders in this category. Software as a service (SAAS): This is the most common form of cloud computing which we see in action. It is a complete software offering on the cloud. They are accessed by the customers on pay per use basis. Saleforce.com s CRM, Google apps etc are the prime example of such a service. Salesforce.com s CRM, Gmail and Hotmail are prime examples of SAAS. IX. CLOUD STORAGE Cloud storage is a model of networked computer data storage where data is stored on multiple virtual servers, generally hosted by third parties, rather than being hosted on dedicated servers. Hosting companies operate large data centers; and people who require their data to be hosted buy or lease storage capacity from them and use it for their storage needs. The data center operators, in the background, virtualize.the resources according to the requirements of the customer and expose them as virtual servers, which the customers can themselves manage. Physically, the resource may span across multiple servers. X. SECURITY The relative security of cloud computing services is a contentious issue which may be delaying its adoption. Issues barring the adoption of cloud computing are due in large part to the private and public sectors unease surrounding the external management of security based services. It is the very nature of cloud computing based services, private or public, that promote external management of provided services. This delivers great incentive amongst cloud computing service providers in producing a priority in building and maintaining strong management of secure services. Organizations have been formed in order to provide standards for a better future in cloud computing services. One organization in particular, the Cloud Security Alliance is a non-profit organization formed to promote the use of best practices for providing security assurance within cloud computing. Security is always a concern, especially when running environments like windows that are so familiar the world over. Microsoft has a reasonable patch management solution but now in the cloud this effectively can be delivered in minutes rather than days.in many cases, some organizations have the view that cloud solutions outsourcing and managed services are less secure. What the company is failing to recognize is that they are probably already using such services without consideration. Services like Blackberry, Message labs and other such services involve messages being sent to a third party, scanned then forwarded back into the organizations localized mail stream. This would undoubtedly change most people s perspective as a well run cloud solution far outweighs the perception of insecurity and loss of control. In fact, in many cases the solution is to build better hardware, firmer controls and more efficient infrastructure at a lower cost. XI.PROS AND CONS OF CLOUD COMPUTING Cloud computing can enable the constant flow of information between the outsourced service and the outsourcing service. Other remote systems would struggle with such a task because they are based on database communications that are largely outdated. The ease with which the information can be accessed gives confidence to the employees of the outsourcing organization that they can continue with their normal work despite the introduction of cloud computing. The pay as you go model of cloud computing adds considerable savings potential to the company s portfolio. One of the issues that concerns managers is the impact of idle time on the overall cost of information technology. If you are using an external entity for the management of the IT portfolio, then you can write an agreement that will only charge you for when you use the IT facilities. The main problems with cloud computing are related to the loss of control to another party. This can lead to supervision problems and conflict within the information technology departments. You will have to set up new systems for dealing with this conflict and you will have ISSN: Page 807

6 to configure your communication systems on the basis that there is another company involved in your business. Sometimes cloud computing will have so many teething problems that it might take years before you settle into an agreement with your supplier whereby conflicts can be resolved before they escalate. XII.BENEFITS OF CLOUD COMPUTING There are many benefits to a cloud solution, but these need to be weighed and understood before opting for a solution that is partially out of the IT departments control. Below we will cover some of the benefits, components and countermeasures that need to be understood before opting in. Greener: Cloud solutions tend to be greener, as some of the infrastructure is co hosted and shared, some of the applications and solutions are fully virtualized and other design changes make the whole offering more efficient and thus greener. In the UK, if an enterprise hosts a typical exchange server, the electrical costs usually add up to over 500 per year. A collocated server with similar specification and computing power would cost less than half this in the cloud. Then there is the question of licensing. Typical vendor licensing cost can vary based on size of enterprise. In most cases, service providers have cumulative packages that make the full cloud subscription cheaper for the consumer as the service providers have better deals with vendors. In turn, the cloud delivered solution is much cheaper from a hosting and licensing perspective. The skills are also cumulative so the customer benefits from enhanced expert skill. solution. This would make the cost prohibitive and most organizations would not consider this solution; however this is exactly what happened in the beginning of the cell phone service 15 years ago, and how the offering was funded. Today, the cost of mobile telephony has dropped and become affordable. Evidently, people now subscribe without a second thought and this is a fully managed, wireless cloud type service funded by subscription and the numbers. XIII.CLOUD COMPUTING IN FUTURE In the future, more cloud adoption is certain, this year alone the move to the cloud by many business has been phenomenal, so much so that some cloud business have grown by over 200%. Large vendors see this as the growing model for software and services in the future so more focus by the vendors is afforded. Do not be surprised if the cloud bursts with offerings over the next 24 months. XIV.REFERENCES [1] T Velte, A Velte, R Elsenpeter dl.acm.org [2] P Mell, T Grance - NIST special publication, predeveloper.att.com [3] L Youseff, M Butrico, D Da Silva - Grid Computing, ieeexplore.ieee.org [4] R Buyya, CS Yeo, S Venugopal, J Broberg - Future Generation, Elsevier [5] M Armbrust, A Fox, R Griffith, AD Joseph - Communications of the, dl.acm.org Most managed services are looked after by dedicated teams per solution. This means that the solution is built by specialists that focus on the particular technology. The outcome is that the offering is more streamlined and a service runs within the best practice guidelines of the vendor and industry. This would be markedly different compared to home or internally built enterprise solutions that cannot emulate the level of a cloud service. Centralized: The centralized yet potentially decentralized management solution. This fully scalable and flexible cloud solution offers something that is difficult to achieve for most large enterprises. Compared to locally hosted applications a cloud solution would offer company flexibility and reach that any global business would envy. This is very compelling, and on many occasions, this feature can be the sole reason for an organization to move into the cloud. Affordable: One of the important considerations to a cloud service is cost. Imagine having to pay for all the cell phone towers used every time you wanted to buy a mobile phone. This would mean that to use the infrastructure, an individual or enterprise would have to pay for the towers, the connectivity between them and all the other elements of the ISSN: Page 808