Cloud computing from A to Z

From Amazon EC2 to Windows Azure, we define the terms you need to know in this cloud computing glossary.

This cloud computing glossary is a compilation of the most important terms commonly used in the cloud market.

From Amazon's Elastic Compute Cloud to Microsoft's Windows Azure, we've collected the best cloud definitions to provide a one-stop resource for anyone on the lookout for a cloud computing reference tool.

As cloud computing continues to expand, we'll add more terms and definitions. If you think there's something glaring that we left out, be sure to let us know.

Cloud computing glossary, A-Z
A | C | E | F | G | H | I | M | P | R | S | V | W


Amazon Elastic Compute Cloud (EC2): Amazon's EC2 is a cloud computing service that allows users to deploy and run their applications on rented virtual computers. Users can boot what are called Amazon Machine Images and create an instance, also known as a virtual machine, and pay for the amount of computing power they need by the hour. Amazon EC2 uses Xen virtualization, and the service allows users to adapt to changing performance and capacity needs with an auto-scaling function.

See also: Getting started with Amazon EC2

Amazon Simple Storage Service: Amazon's S3 is a cloud storage service that provides scalable, unlimited online archiving and backup for Amazon Web Services users. As of early March, Amazon S3 had stored more than 100 billion objects.

See also: Cloud storage defined

Application programming interface (API): An API is set of programming instructions that cloud computing providers release to developers in order to allow for the creation and deployment of applications on their cloud services. APIs are software-to-software interfaces that accelerate the application development process.

See also: Our cloud computing programming API tutorial


Cloud backup: Cloud backup is the concept of sending copies of your data to an off-site server for backup storage. Enterprises have proven reluctant to adopt cloud backup for pertinent data, as security concerns and fears about storing critical information in the cloud persist. Several prominent cloud backup services are Amazon S3, Asigra and EMC's Mozy.

See also: Backup to the compute cloud

Cloud cartography: Cloud cartography is a strategy designed to pinpoint the physical locations of Web servers hosted on a third-party cloud computing service. The goal would be to map the service provider's infrastructure in order to identify where a particular virtual machine resides. This scheme was discovered during a study carried out on Amazon Web Services by researchers from MIT and the University of California, San Diego.

See also: Virtualization vulnerabilities leave clouds insecure

Cloud Security Alliance: The Cloud Security Alliance (CSA) is an organization created to promote security best practices for cloud computing providers. Headed by executive director Jim Reavis and technical director Chris Hoff, the CSA claims such prominent members as AT&T, CA, Cisco, Google, Rackspace and Microsoft.

See also: Cloud Security Alliance creating cloud provider seal of approval


Elasticity: Elasticity in cloud computing refers to the ability of a provider or an application to grow and shrink the amount of IT infrastructure as needed to meet demand. Elasticity is considered a key cloud feature because it reduces the need of an organization to carry overhead or spare capacity.

See also: The elasticity factor: How CIOs are hedging IT budgets and hiring

F is the Platform as a Service offering from With Apex Code,'s on-demand programming language, developers can create hosted applications and integrate client-side applications with Apex-based hosted components.

See also: Developers discuss pros and cons of


Google App Engine: Google App Engine is the Platform as a Service offering from the search giant. The development platform is free up to a certain level of used resources; fees are then charged for additional storage, bandwidth or CPU cycles. Targeted at Web developers and Web hosting applications, the only programming languages currently supported by App Engine are Python and Java.

See also: Running a Web service on Google App Engine


Hybrid cloud: A hybrid cloud is a cloud model that combines the advantages of public and private cloud computing environments. The popularity of hybrid clouds continues to grow as enterprises look to maintain the reliability of in-house data security while still benefiting from the scalability of public cloud.

See also: From private cloud to hybrid cloud: Six things to consider


Infrastructure as a Service: Infrastructure as a Service (IaaS) is a pay-per-use service where a cloud computing provider offers storage space, software and network equipment as consumable resources. IaaS offerings include Amazon EC2, GoGrid and the Rackspace Cloud.

See also: Infrastructure as a Service -- How to maintain control


Multi-tenancy: Multi-tenancy is the ability of one platform or piece of computing infrastructure to hold more than one application, virtual machine or process at a time, for multiple users. A cloud computing envrionment that is accessible to all users defines a multi-tenant environment.

See also: SAP adds to the SaaS multi-tenancy debate


Platform as a Service: Platform as a Service (PaaS) is a cloud computing model through which a computing platform is delivered to users via the Web. PaaS is often used for the development, deployment and hosting of applications. PaaS offerings include Microsoft Azure, and Google App Engine.

See also: How to use Platform as a Service securely

Private cloud: Private cloud is an in-house cloud computing option that offers hosted services to a limited number of people from behind an organization's firewall. Enterprises are showing greater and greater interest in private clouds, as concerns about cloud computing security have led many organizations to value the dependability of an on-premise cloud option.

See also: Want to build a private cloud?

Public cloud: Public cloud is any third-party service that offers storage and computing power over the Internet in a scalable, pay-per-usage fashion. Despite being the standard cloud computing model, the enterprise has been slow to accept public cloud over private cloud due to questions about security and compliance issues.

See also: Five requirements for deploying an application in a public cloud


Rackspace Cloud: Rackspace Cloud, which includes the Cloud Files storage service and Cloud Servers infrastructure service, is the hosting provider's public cloud computing offering. Headed up by president and CSO Lew Moorman, Rackspace's cloud service does battle with behemoth Amazon Web Services by promising "fanatical support to its committed group of users."

See also: Rackspace attempts to retool hosting into cloud

RightScale Cloud Management Platform: The Cloud Management Platform is the crown jewel in RightScale's collection, a multi-provider cloud management service that runs on both Amazon Web Services and Rackspace. With founder and CTO Thorsten von Eicken at the helm, RightScale has its hand in more cloud computing matters than arguably any other company.

See also: RightScale users sound off on cloud pros and cons


Scalability: Scalability in cloud computing refers to the ability of a provider or an application to instantly and automatically provision compute capacity to meet spikes in demand.

See also: Cloud computing -- Does IT scalability translate into business agility?

Service-level agreements (SLAs): A service-level agreement is the contract that quantifies what the vendor's service must present and guarantees the customer certain service-related percentages and benchmarks. In situations involving cloud computing, SLAs promise certain cloud-based costs and ensure acceptable levels of service availability.

See also: Making sense of cloud-based SLAs

Software as a Service: Software as a Service (SaaS) is a software distribution model that provides applications to customers via the Internet. The most commonly used form of cloud computing, SaaS continues to grow as Web services and service-oriented architectures advance. The top purveyors of SaaS are NetSuite, Adobe and

See also: How to use Software as a Service securely


VMforce: VMforce is the Java PaaS offering from VMware and Unveiled after much speculation, VMforce is aimed at SaaS and Web services developers. The major components of VMforce are VMware's Spring platform -- and its community of Java developers -- and's platform.

See also: VMforce: What it is, what it means


Windows Azure: Windows Azure is Microsoft's cloud computing platform. Launched in January 2010, Microsoft often updates a list of case studies to show how its numerous customers are using the cloud. Microsoft's cloud platform contains the Azure operating system, the SQL Azure database service and its AppFabric application connectivity service.

See also: An introduction to developing for Azure

Cloud computing glossary, A-Z
A | C | E | F | G | H | I | M | P | R | S | V | W

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