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Amazon Web Services

Amazon was the first providers of cloud computing (http://aws.amazon.com). In August 2006 it declared limited public beta release of its Elastic Computing platform called EC2.

Elastic Compute Cloud (EC2) is a Web service with a smooth interface for launching part of an application under several operating systems, such as Microsoft Windows Server 2003 and Microsoft Windows Server 2008, NetBSD, OpenSolaris, several Linux distributions and FreeBSD.

EC2 enables a user to load instances of an application with a user configured application environment, maintains networks access approvals, and run the images using as many or as few systems as desired. EC2 instances boot from an Amazon Machine Image that is digitally signed and stored in S3; one could use the few images provided by Amazon or customize an image and store it in S3.

A user can,

lunch an instance from an existing AMI and terminate an instance
start and stop an instance;
create a new image;
add tags to identify an image; and
reboot an instance.

EC2 is based on the Xen virtualization strategy. In EC2 each virtual machine functions as a virtual private server and is called an instance; an instance indicate the maximum amount of resources available to an application, the interface for that instance, as well as, the cost per hour. This is a web service that provides resizable computing capacity in the cloud. It is designed in order to make web-scale computing easier for different developers and presents many advantages to customers:

It is a web service interface that allows customers to obtain and configure capacity with minimal effort.
It provides users with complete control of their rented computing resources and lets them run on a proven computing environment.
It reduces the time required to access and boot new server instances to minutes, allowing customers to quickly scale capacity as their computing needs edict.
It changes the computing economics by allowing clients to pay only for space they actually use.
It provides developers the tools necessary for building failure-proof applications and isolate themselves from common failure scenarios.

Amazon EC2 display a true virtual computing environment,that allows clients to use a web-based interface to gain and manage the services needed for launching one or more occurrence of a various OS. Clients can load the OS settings with their customized applications. clients can manage their network’s access previlage and run as many or as few systems as required. For using Amazon EC2,first clients need to create an Amazon Machine Image (AMI). The machine image contains the applications,data, libraries, and associated arrangement settings used in the virtual computing atmosphere. Amazon EC2 to get up and running immediately offers use of preconfigured images built with templates. Once users defines and configures their AMI, they use the Amazon EC2 tools provided for keeping the AMI by uploading the AMI into Amazon S3. Amazon S3 safe, reliable, and fast access to a client AMI. Amazon s3 is a repository. Clients must use the Amazon EC2 web service to configure security and network access before using AMI.

In order connect to a virtual machine in a cloud,IP address must be known by the client. Public IP addresses are mapped internally to private IP addresses due to security reasons. For example, a virtual machine that runs under Amazon’s EC2 has different IP addresses:

EC2 Private IP Address
It is an internal address of an instance that can only be used internally.
EC2 Public IP Address
Network traffic rising outside the EC2 network must be able to use either the public or elastic IP address of the instance. The public IP address is interpreted using the (NAT) to the private IP address when an item is launched and it is valid until the instance it terminates. Traffic to the public address is forwarded to the Instance's private IP address .
EC2 Elastic IP Address
The IP address allot to an AWS EC2 account and used by traffic growing from outside the EC2 cloud. NAT is used to map an elastic IP address to the private IP address. Elastic IP addresses allow the cloud user to cover instance or availability zone failures by programmatically re-mapping a public IP addresses to any instance related with the user’s account. This allows fast recovery after a system failure;

Amazon EC2 Service Characteristics:

Dynamic Scalability
Amazon EC2 allows users to increase or decrease capacity within minutes. Users can call a single instance, hundreds of instances, or even thousands of instances together. Of course, because this is all regulated with web service APIs, applications can naturally scale itself up or down depending on its demands. This type of progressive scalability is very appealing to enterprise customers because it enables them customers to meet their customer's’ needs without having to overbuild their framework.
Full Control of Instances
Users have total control of their instances. They have core access to each instance and also can interact with them as one would interact with any machine. Instances can be restarted remotely using web service APIs available. Once a user sets up their account and uploads their AMI to the Amazon S3 service, they just need to start that instance. It is possible to boot an AMI on any number or type of instances by calling the API RunInstances, provided by Amazon.
Configuration Flexibility
Configuration settings can differ extensively among users. They have the choice of number of instance types, software packages and operating systems. Amazon EC2 allows users to select a configuration of memory, CPU, and instance storage that is best for choice of their operating system and application. For example, a user’s choice of operating systems may also include Linux, windows or even solaris all running on virtual servers.
Integration with Other Amazon Web Services
Amazon EC2 does its work in combination with a diversity of other Amazon web services. For example Amazon Simple Queue Service, Amazon S3, Amazon CloudFront and Amazon SimpleDB are all joined to provide a complete solution for query processing,storage and computing across a wide range of applications. Amazon S3 yield a web services interface that enables users to store and fetch any amount of data from the Internet at any where at any time.. It gives developers straightforward access to the same highly reliable, scalable, fast , cheaper data storage infrastructure that Amazon uses to run its own universal network of web sites. Amazon SimpleDB is a amazon web-based service, designed for running different queries on structured data stored with the Amazon S3 in real time. This service works in combination with the Amazon EC2 to provide users the ability to query. Store and process data sets within the cloud. To make web-scale computing easier and more cost effective for developers these services are designed. Amazon Simple Queue Service (Amazon SQS) is a scalable, reliable and hosted sequence for storing messages as they pass between different computers. Developers can move data using Amazon SQS between different distributed components of applications that perform different types of tasks without losing any messages or requiring complete availability for every component. Amazon CloudFront is a content delivery web service. It coordinate with other Amazon web services to circulate content to end users with low abeyance and high speed data transfer. Contents are delivered using a global network of edge locations in Amazon CloudFront. Requests for objects are automatically transmitted to the nearest edge server, so content is delivered with the best performance possible. A request from the user’s computer is received by an edge server and makes a connection to another computer where application resides called the origin server.
Reliable and Resilient Performance Amazon Elastic Block Store (EBS)
Amazon EBS offers continuous storage for Amazon EC2 occurrence. Amazon EBS volumes provide “off-instance” storage that carry on independently from the life of any instance. Amazon EBS volumes are highly reliable, highly available data shares that can be connected to a running Amazon EC2 instance and are uncovered to the instance as regular block devices. Amazon EBS volumes are automatically reproduced on the back. The service provides users with the capability to create point-in-time photograph of their data volumes, stored using the Amazon S3 service. These photograph can be used as a starting stage for new Amazon EBS volumes and can protect data continually.
Support for Use in Geographically Disparate Locations
Users are provided with the ability to place multiple instances in multiple locations. Amazon EC2 locations are collected of Regions and Availability Zones. Regions comprises of multiple availability Zones, are geographically scattered, and are in independent geographic areas or countries. Availability Zones are noticeable locations that are engineered to be secluded from failures in other Availability Zones and provide cheap, low-latency network connectivity to other Availability Zones in the same Region. Amazon EC2 is currently available in two regions, the United States and Europe.



Cloud computing for dummies, Judith hurwitz, Robin Bloor, MarciaKaufman, Fern Halper
Cloud computing: Theory and practices, Dan c. marinescu


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