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Cloud Computing: a Perspective Study
Lizhe WANG, Gregor VON LASZEWSKI Service Oriented Cyberinfrastruture Lab, Rochester Inst. of Tech. 102 Lomb Memorial Drive, Rochester, NY 14623, U.S.
{Lizhe.Wang, Laszewski}@gmail.com Marcel KUNZE, Jie TAO Steinbuch Centre for Computing, Karlsruhe Institute of Technology Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, Germany
{Marcel.Kunze, Jie.Tao}@iwr.fzk.de
Received 1 Dec 2008
Abstract The Cloud computing emerges as a new computing paradigm
which aims to provide reliable, customized and QoS guaranteed dynamic computing environments for end-users. In this paper, we study the Cloud computing paradigm from various aspects, such as definitions, distinct features, and enabling technologies. This paper brings an introductional review on the Cloud computing and provide the state-of-the-art of Cloud computing technologies.
Keywords Cloud Computing, Grid Computing, Cyberinfrastructure, Distributed Computing
§ 1 Introduction
The Cloud computing, which was coined in late of 2007, currently emerges as a hot topic due to its abilities to offer flexible dynamic IT infrastructures, QoS guaranteed computing environments and configurable software services. As re- ported in the Google trends shown in Figure 1, the Cloud computing (the blue
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Fig. 1 Cloud computing in Google trends
line), which is enabled by virtualization technology (the yellow line), has already outpaced the Grid computing 8)^ (the red line). Numerous projects within industry and academia have already started, for example the RESERVOIR project 27)^ – an IBM and European Union joint research initiative for Cloud computing, Amazon Elastic Compute Cloud 13)^ , IBM’s Blue Cloud 10), scientific Cloud projects such as Nimbus 24)^ and Stratus 31)^ , and OpenNEbula 26)^. HP, Intel Corporation and Yahoo! Inc. recently announced the creation of a global, multi-data center, open source Cloud computing test bed for industry, research and education 3)^. There are still no widely accepted definitions for the Cloud comput- ing albeit the Cloud computing practice has attracted much attention. Several reasons lead into this situation:
- Cloud computing involves researchers and engineers from various back- grounds, e.g., Grid computing, software engineering and database. They work on Cloud computing from different viewpoints.
- Technologies which enable the Cloud computing are still evolving and progressing, for example, Web 2.0 and Service Oriented Computing.
- Existing computing Clouds still lack large scale deployment and usage, which would finally justify the concept of Cloud computing. In this paper we attempt to contribute the concept of Cloud comput- ing: definition, functionality, enabling technology and typical applications. The remaining parts of this paper are organized as follows. Section 2 discusses the concept of Cloud computing, Section 3 presents the functionalities of the Cloud computing, Section 4 reviews the distinct features of the Cloud computing, and
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data center, as a pay-as-you-go subscription service. The HaaS is flexible, scalable and manageable to meet your needs 2)^. Examples could be found at Amazon EC2 13)^ , IBM’s Blue Cloud project 10)^ , Nimbus 24), Eucalyptus 18)^ and Enomalism 17)^.
Software as a Service (SaaS): Software or an application is hosted as a service and provided to cus- tomers across the Internet. This mode eliminates the need to install and run the application on the customer’s local computers. SaaS therefore alleviates the customer’s burden of software maintenance, and reduces the expense of software purchases by on-demand pricing. An early example of the SaaS is the Application Service Provider (ASP) 15)^. The ASP approach provides subscriptions to software that is hosted or delivered over the Internet. Microsoft’s “Software + Service” 30)^ shows another example: a combination of local software and Internet services interacting with one another. Google’s Chrome browser 21)^ gives an interesting SaaS scenario: a new desktop could be offered, through which applications can be delivered (either locally or remotely) in addition to the traditional Web browsing experience.
Data as a Service (DaaS): Data in various formats and from multiple sources could be accessed via services by users on the network. Users could, for example, ma- nipulate the remote data just like operate on a local disk or access the data in a semantic way in the Internet. Amazon Simple Storage Service (S3) 14)^ provides a simple Web ser- vices interface that can be used to store and retrieve, declared by Amazon, any amount of data, at any time, from anywhere on the Web. The DaaS could also be found at some popular IT services, e.g., Google Docs 22)^ and Adobe Buzzword 12)^. ElasticDrive 16)^ is a distributed remote storage application which allows users to mount a remote storage resource such as Amazon S3 as a local storage device.
Based on the support of the HaaS, SaaS and DaaS, the Cloud computing in addition can deliver the Infrastructure as a Service (IaaS) for users. Users thus can on-demand subscribe to their favorite computing infrastructures with requirements of hardware configuration, software installation and data access demands. Figure 2 shows the relationship between the services. The Google
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App Engine 20)^ is an interesting example of the IaaS. The Google App Engine enables users to build Web applications with Google’s APIs and SDKs across the same scalable systems, which power the Google applications.
SaaS (^) HaaS DaaS
Cloud resoruce
Application
Scientific Cloud
IaaS
Fig. 2 Cloud functionalities
§ 4 Why is Cloud Computing Distinct?
The Cloud computing distinguishes itself from other computing paradigms, like Grid computing, Global computing, Internet Computing in the following as- pects:
User-centric interfaces. Cloud services should be accessed with simple and pervasive methods. In fact, the Cloud computing adopts the concept of Utility comput- ing. In other words, users obtain and employ computing platforms in computing Clouds as easily as they access a traditional public util- ity (such as electricity, water, natural gas, or telephone network). In detail, the Cloud services enjoy the following features:
- The Cloud interfaces do not force users to change their working habits and environments, e.g., programming language, com- piler and operating system. This feature differs Cloud comput- ing from Grid computing as Grid users have to learn new Grid commands & APIs to access Grid resources & services.
- The Cloud client software which is required to be installed lo- cally is lightweight. For example, the Nimbus Cloudkit client
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eral state-of-the-art techniques are identified here:
Virtualization technology. Virtualization technologies partition hardware and thus provide flex- ible and scalable computing platforms. Virtual machine techniques, such as VMware 34)^ and Xen 1), offer virtualized IT-infrastructures on demand. Virtual network advances, such as VPN 7)^ , support users with a customized network environment to access Cloud resources. Virtualization techniques are the bases of the Cloud computing since they render flexible and scalable hardware services.
Orchestration of service flow and workflow. Computing Clouds offer a complete set of service templates on de- mand, which could be composed by services inside the computing Cloud. Computing Clouds therefore should be able to automatically orchestrate services from different sources and of different types to form a service flow or a workflow transparently and dynamically for users.
Web service and Service Oreinted Architecture (SOA). Computing Cloud services are normally exposed as Web services, which follow the industry standards such as WSDL 33), SOAP 28)^ and UDDI 25). The services organization and orchestration inside Clouds could be managed in a Service Oriented Architecture (SOA). A set of Cloud services furthermore could be used in a SOA application envi- ronment, thus making them available on various distributed platforms and could be further accessed across the Internet.
Web 2.0. Web 2.0 is an emerging technology describing the innovative trends of using World Wide Web technology and Web design that aims to enhance creativity, information sharing, collaboration and functional- ity of the Web 6)^. The essential idea behind Web 2.0 is to improve the interconnectivity and interactivity of Web applications. The new paradigm to develop and access Web applications enables users access the Web more easily and efficiently. Cloud computing services in na- ture are Web applications which render desirable computing services on demand. It is thus a natural technical evolution that the Cloud computing adopts the Web 2.0 technique.
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World-wide distributed storage system. A Cloud storage model should foresee:
- A network storage system, which is backed by distributed stor- age providers (e.g., data centers), offers storage capacity for users to lease. The data storage could be migrated, merged, and managed transparently to end users for whatever data for- mats. Examples are Google File System 9)^ and Amazon S3 14)^. A Mashup 11)^ is a Web application that combines data from more than one source into a single integrated storage tool. The SmugMug 29)^ is an example of Mashup, which is a digital photo sharing Web site, allowing the upload of an unlimited number of photos for all account types, providing a published API which allows programmers to create new functionality, and support- ing XML-based RSS and Atom feeds.
- A distributed data system which provides data sources accessed in a semantic way. Users could locate data sources in a large distributed environment by the logical name instead of physical locations. Virtual Data System (VDS) 32)^ is good reference.
Programming model. Users drive into the computing Cloud with data and applications. Some Cloud programming models should be proposed for users to adapt to the Cloud infrastructure. For the simplicity and easy access of Cloud services, the Cloud programming model, however, should not be too complex or too innovative for end users. The MapReduce 4, 5)^ is a programming model and an associated im- plementation for processing and generating large data sets across the Google worldwide infrastructures. The MapReduce model firstly in- volves applying a “map” operation to some data records – a set of key/value pairs, and then processes a “reduce” operation to all the values that shared the same key. The Map-Reduce-Merge 35)^ method evolves the MapReduce paradigm by adding a “merge” operation. Hadoop 23)^ is a framework for running applications on large clus- ters built of commodity hardware. It implements the MapReduce paradigm and provides a distributed file system – the Hadoop Dis- tributed File System. The MapReduce and the Hadoop are adopted by recently created international Cloud computing project of Yahoo!,
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