Tuesday, February 18, 2014

Amazon Web Services --Aws

Amazon Web Services (abbreviated AWS) is a collection of remote computing services (also called web services) that together make up a cloud computing platform, offered over the Internet by Amazon.com. The most central and well-known of these services are Amazon EC2 and Amazon S3. The service is advertised as providing a large computing capacity (potentially many servers) much faster and cheaper than building a physical server farm.
Amazon Elastic Compute Cloud (EC2)  is a central part of Amazon.com's cloud computing platform, Amazon Web Services (AWS). EC2 allows users to rent virtual computers on which to run their own computer applications. EC2 allows scalable deployment of applications by providing a Web service through which a user can boot an Amazon Machine Image to create a virtual machine, which Amazon calls an "instance", containing any software desired. A user can create, launch, and terminate server instances as needed, paying by the hour for active servers, hence the term "elastic". EC2 provides users with control over the geographical location of instances that allows for latency optimization and high levels of redundancy.

Amazon Machine Image (AMI) provides the information required to launch an instance, which is a virtual server in the cloud. You specify an AMI when you launch an instance, and you can launch as many instances from the AMI as you need.
An AMI includes the following:
A template for the root volume for the instance (for example, an operating system, an application server, and applications)
Launch permissions that control which AWS accounts can use the AMI to launch instances
A block device mapping that specifies the volumes to attach to the instance when it's launched

Amazon Simple Storage Service , Amazon S3 is storage for the Internet. It is designed to make web-scale computing easier for developers.
Amazon S3 provides a simple web-services interface that can be used to store and retrieve any amount of data, at any time, from anywhere on the web. It gives any developer access to the same highly scalable, reliable, secure, fast, inexpensive infrastructure that Amazon uses to run its own global network of web sites. The service aims to maximize benefits of scale and to pass those benefits on to developers.

The Ami of an Instance will be running in an storage known as ephemeral, in which none of the datas are stored and once the instance is terminated the Data's or the modification to the instance AMI are lost.

Anything that is not stored on an ebs volume that is mounted to the instance will be lost. For instance, if you mount your ebs volume at /mystuff, then anything not in /mystuff will be lost. If you don't mount an ebs volume and save stuff on it, then I believe everything will be lost.
You can create an AMI from your current machine state, which will contain everything in your ephemeral storage. Then, when you launch a new instance based on that AMI it will contain everything as it is now.
Note that there is a difference between "stop" and "terminate". If you "stop" an instance that is backed by EBS then the information on the root volume will still be in the same state when you "start" the machine again. If you "terminate" the machine, then even if it is backed by EBS it is gone. Creating the AMI will save that state for you and allow you to start a new instance to replace a terminated instance.

Amazon Elastic Block Storage (EBS) provides raw block devices that can be attached to Amazon EC2 instances. These block devices can then be used like any raw block device. In a typical use case, this would include formatting the device with a filesystem and mounting said filesystem. In addition EBS supports a number of advanced storage features, including snapshotting and cloning. Currently EBS volumes can be up to 1TB in size. EBS volumes are built on replicated back end storage, so that the failure of a single component will not cause data loss.

Amazon CloudWatch provides monitoring for AWS cloud resources and the applications customers run on AWS.Amazon CloudWatch monitors AWS resources such as Amazon EC2 and Amazon RDS DB instances, and can also monitor custom metrics generated by a customer’s applications and services. With Amazon CloudWatch, you gain system-wide visibility into resource utilization, application performance, and operational health.
Amazon's elastic IP address feature is similar to static IP address in traditional data centers, with one key difference. A user can programmatically map an elastic IP address to any virtual machine instance without a network administrator's help and without having to wait for DNS to propagate the new binding. In this sense an Elastic IP Address belongs to the account and not to a virtual machine instance. It exists until it is explicitly removed, and remains associated with the account even while it is associated with no instance.

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