A Simple Introduction to Cloud Computing

A Simple Introduction to Cloud Computing

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. This cloud model promotes availability and is composed of five essential characteristics, three service models, and four deployment models.

Essential Characteristics:

  1. On-demand self-service. A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service’s provider.
  2. Broad 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).
  3. Resource pooling. The provider’s computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence in that the customer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). Examples of resources include storage, processing, memory, network bandwidth, and virtual machines.
  4. Rapid elasticity. Capabilities can be rapidly and elastically provisioned, in some cases automatically, to quickly scale out and rapidly released to quickly scale in. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be purchased in any quantity at any time.
  5. Measured Service. Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported providing transparency for both the provider and consumer of the utilized service.

Service Models:

  1. Cloud Software as a Service (SaaS). The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based email). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.
  2. Cloud Platform as a Service (PaaS). The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations.
  3. Cloud Infrastructure as a Service (IaaS). The capability provided to the consumer is to provision 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 limited control of select networking components (e.g., host firewalls).

Deployment Models:

  1. Private cloud. The cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on premise or off premise.
  2. Community 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). It may be managed by the organizations or a third party and may exist on premise or off premise.
  3. Public cloud. The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.
  4. Hybrid cloud. The cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load-balancing between clouds).

Types of cloud computing

Cloud computing is typically classified in two ways:

  1. Location of the cloud computing
  2. Type of services offered

Location of the cloud

Cloud computing is typically classified in the following three ways:

  1. Public cloud: In Public cloud the computing infrastructure is hosted by the cloud vendor at the vendor’s premises. The customer has no visibility and control over where the computing infrastructure is hosted. The computing infrastructure is shared between any organizations.
  2. Private cloud: The computing infrastructure is dedicated to a particular organization and not shared with other organizations. Some experts consider that private clouds are not real examples of cloud computing. Private clouds are more expensive and more secure when compared to public clouds. Private clouds are of two types: On-premise private clouds and externally hosted private clouds. Externally hosted private clouds are also exclusively used by one organization, but are hosted by a third party specializing in cloud infrastructure. Externally hosted private clouds are cheaper than On-premise private clouds.
  3. Hybrid cloud Organizations may host critical applications on private clouds and applications with relatively less security concerns on the public cloud. The usage of both private and public clouds together is called hybrid cloud. A related term is Cloud Bursting. In Cloud bursting organization use their own computing infrastructure for normal usage, but access the cloud using services like Salesforce cloud computing for high/peak load requirements. This ensures that a sudden increase in computing requirement is handled gracefully.
  4. Community cloud involves sharing of computing infrastructure in between organizations of the same community. For example all Government organizations within the state of California may share computing infrastructure on the cloud to manage data related to citizens residing in California.

Classification based upon service provided

Based upon the services offered, clouds are classified in the following ways:

  1. Infrastructure as a service (IaaS) involves offering hardware related services using the principles of cloud computing. These could include some kind of storage services (database or disk storage) or virtual servers. Leading vendors that provide Infrastructure as a service are Amazon EC2, Amazon S3, Rackspace Cloud Servers and Flexiscale.
  2. Platform as a Service (PaaS) involves offering a development platform on the cloud. Platforms provided by different vendors are typically not compatible. Typical players in PaaS are Google Application Engine, Microsofts Azure, Salesforce.com force.com .
  3. Software as a service (SaaS) includes a complete software offering on the cloud. Users can access a software application hosted by the cloud vendor on pay-per-use basis. This is a well-established sector. The pioneer in this field has been Salesforce.coms offering in the online Customer Relationship Management (CRM) space. Other examples are online email providers like Googles gmail and Microsofts hotmail, Google docs and Microsofts online version of office called BPOS (Business Productivity Online Standard Suite).

The above classification is well accepted in the industry. David Linthicum describes a more granular classification on the basis of service provided. These are listed below:

  1. Storage-as-a-service
  2. Database-as-a-service
  3. Information-as-a-service
  4. Process-as-a-service
  5. Application-as-a-service
  6. Platform-as-a-service
  7. Integration-as-a-service
  8. Security-as-a-service
  9. Management/Governance-as-a-service
  10. Testing-as-a-service
  11. Infrastructure-as-a-service

Free Cloud Computing Applications

There are a large number of interesting cloud computing applications that are completely free. In these Software as a Service (SaaS) applications processing happens on the data centers hosted by these organizations. Unlike standard desktop applications, no processing happens on the desktops. Here we take a look at the cloud computing applications that are available for free. The sites have been listed below:

Photo Editing Software

Picnik is a popular free online photo editing software. It has features like cropping, resizing and rotation of images, addition of special effects. A premium version of Picnik with advanced features is available for $24.95 a year.

Pixlr is a free online photo editing software. Pixlr combines image design and paint tools with photo editing and adjustment features. It lets users edit brightness/contrast, and has the ability to crop and layer photos. Even though Pixlr has many complex features, the software is relatively simple to use.

Online file storage

MediaFire is a leading online file storage site. MediaFire may be used to host, share any files including documents, images, presentations, videos. The interface is easy to use. The free version of MediaFire includes unlimited disk space and unlimited uploads/downloads. The only limit in the free version is on the file size - the maximum file size allowed is 200 MB. The files may be organized into folders.

Megaupload is another popular file storage site. The feature set is similar to mediafire. There is a limit of 200 GB disk space and 2 GB limit on file size in the free account. There is also a waiting time of 25 secs before each download begins in the free version. The premium version has none of the above limitations in addition to better download speed and unlimited disk speed. The charges for premium version is $9.99 per month.

hotfile offers a free version of online file sharing application with a maximum file size of 400Mb. Monthly charges for premium version are $9 per month. The premium version includes higher speed on downloads, unlimited parallel downloads and downloading without waiting time and advertising.

4Shared is yet another popular online file sharing software. The free version provides a maximum file download size of 200MB and over all disk space of 10 GB. Premium version provides 100GB of disk space, and a maximum file size of 5GB.

Other popular online file sharing applications are Rapidshare, depositfiles, Yourfilehost, zshare, NowDownloadAll, easy-share, Imgur and Uploading.

Twitter Related Applications

bit.ly converts any URL into a unique short URL. When a user visits the newURL, bit.ly redirects the browser to the real web site. Bit.ly has parternered with Twitter, to allow twitter users to use shortened URLs. This has led to exponential growth of bit.ly URLs. As an example the URL for thecloudtutorial is http://bit.ly/4siQfX .

Twitpic is an application that allows user to upload pictures to be linked from twitter. It uses twitters login, creates shorterened URLs, that can be invoked from twitters microblogging.

Digital Video

Hulu offers videos online for free. Users can download popular movies, TV shows and documentaries and view them on the browser. Hulu allows websites to embed content on their web sites also. Hulu is a joint venture of NBC Universal, Fox Entertainment Group and ABC Inc. At present Hulu's contents can only be viewed in the USA. Other popular online video sites are youtube, WatchMoviesOnline, break.com and Google Video.

Creating Your Image Album

A large number of wonderful sites are available for hosting images on the web. The best ones are flickr, Fotolog, photobucket, webshots, imagebam and ziddu. These sites allow users to organize images into albums, tag them and create slideshows.

Anti-virus Applications on the Web

Cloud Antivirus is an anti virus application on the cloud by a Spanish company Panda Security. It provides functionality to keep virus away from a clean system and also detect and fix a system infested with malware. PC World rates it as the best free anti-virus software. The antivirus can be downloaded onto the machine. The locally installed Cloud Anitvirus sends information about files to the data center on the cloud which checks for malware in the files.

Editing Documents, Spreadsheets and Powerpoints

SlideRocket is an online application that allows users to create presentation. The free version has a disk space storage of 250 MB. It allows importing of PowerPoint presentations. Since it is a web based application, the presentations can be accessed from any location.The free version does not allow users to edit presentations offline.

writeboard is an online free document editor from 37signals. Multiple users can edit the same document, and versions of documents are saved. Writeboard allows users to compare different versions of documents. One limitation of WriteBoard is that it does not support importing Word files.

Slideshare allows users to upload presentations. The site has a huge repository of presentations and is a leading source of free presentations on the web. Documents are available on virtally any topic that one may be able to think off.

Finding Your Way on a Map

Another area where web applications became popular in Web 1.0 was finding directions on the web. The leading sites are mapquest, Google Maps and Yahoo Maps. These have provided million of people maps and directions and helped people get to their destinations over the last decade.

Miscellaneous Free Software as a Service Applications

XE provides foreign exchange tools and services online. Functionality provided includes trading currency and checking exchange rates.

One of the first usages of free software as service applications is checking the status of letters and packages. United States Postal Service, UPS and Fedex all provide free online tracking of packages.