Getting Started with Amazon EC2

Amazon EC2 :

Amazon EC2 is a web service that provides secure, resizable compute capacity in the cloud. With this service, you can provision virtual servers called EC2 instances. With Amazon EC2, you can do the following:

• Provision and launch one or more EC2 instances in minutes.

• Stop or shut down EC2 instances when you finish running a workload.

• Pay by the hour or second for each instance type (minimum of 60 seconds).

You can create and manage EC2 instances through the AWS Management Console, AWS CLI, AWS SDKs, automation tools, and infrastructure orchestration services. To create an EC2 instance, you must define the following:

• Hardware specifications: CPU, memory, network, and storage

• Logical configurations: Networking location, firewall rules, authentication, and the operating system of your choice

Amazon Machine Image :

When launching an EC2 instance, the first setting you configure is which operating system you want by selecting an Amazon Machine Image (AMI).

In the traditional infrastructure world, spinning up a server consists of installing an operating system from installation disks, drives, or wizards over the network. In the AWS Cloud, the operating system installation is not your responsibility. Instead, it's built into the AMI that you choose.

Relationship between AMIs and EC2 instances : EC2 instances are live instantiations (or versions) of what is defined in an AMI, as a cake is a live instantiation of a cake recipe. If you are familiar with software development, you can also see this kind of relationship between a class and an object. In this case, the AMI is how you model and define your instance. The EC2 instance is the entity you interact with, where you can install your web server and serve your content to users. When you launch a new instance, AWS allocates a virtual machine that runs on a hypervisor. Then the AMI that you selected is copied to the root device volume, which contains the image that is used to boot the volume. In the end, you get a server that you can connect to and install packages and additional software on. In the example, you install a web server along with the properly configured source code of your employee directory application.

Configuring EC2

Now that you know how to select an operating system for your EC2 instance, you are ready to choose other configurations to create your EC2 instance, such as the instance type, network, and storage. For an application like the employee directory application, you need instances with enough capacity to process customer requests. Your instance sizing will depend on both the demands of your application and the anticipated size of your user base.
Forecasting server capacity for an on-premises application requires difficult decisions involving significant upfront capital spending. In contrast, changes to the allocation of your cloud-based services can be made with a simple API call. Because of the AWS pay-as-you-go model, you can match your infrastructure capacity to your application’s demand, instead of the other way around.

Amazon EC2 instance types

EC2 instances are a combination of virtual processors (vCPUs), memory, network, and, in some cases, instance storage and graphics processing units (GPUs). When you create an EC2 instance, you need to choose how much you need of each of these components.

Architecting for high availability

In the network, your instance resides in an Availability Zone of your choice. As you learned previously, AWS services that are scoped at the Availability Zone level must be architected with high availability in mind.
Although EC2 instances are typically reliable, two are better than one, and three are better than two. Specifying the instance size gives you an advantage when designing your architecture because you can use more smaller instances rather than a few larger ones.