The Amazon Elastic Compute Cloud (EC2) is an infrastructure as a service (IaaS) cloud. This means that it provides computing power and resources that you can use for a fee. You take care of running the software; Amazon EC2 provides the hardware.
To understand Amazon EC2, it’s important to understand the concept of virtualization. When you use your computer at home, it’s very likely that you have one physical “box” sitting on or below your desk, with a power button, disk drives, a video card, and so on. The relationship between the physical machine and the machine you log into is 1 to 1. Virtualization, however, is the idea of hosting multiple “virtual machines” on a single physical box. These virtual machines share some hardware resources, but they appear to the end user as distinct machines that can be logged into and administered separately.
You may have used virtual machines at your place of employment; many companies are using them in the workplace because they are more flexible and cost efficient. Most often, an IT administrator will purchase or choose a powerful machine and configure it to be a “virtual server”, which is a physical machine that hosts multiple virtual machines. Obviously, it takes a powerful computer to act as a virtual server, and it takes a fair amount of IT administration skill to set one up.
Enter Amazon EC2. When you work with Amazon EC2, you create and run virtual machines in Amazon’s data centers. You don’t have to know too much about the details of the virtual servers (nor does Amazon want to reveal this). The idea is that you can focus on the software on your server and let Amazon take care of the hardware needs.
Of course, there is a cost for using these resources. You are charged hourly fees for the computing power used, and for the amount of data that you store on Amazon EC2. Most of the things you can do or use on Amazon EC2 have some sort of fee associated with them, but unless you are running a high-traffic site with many gigabytes of data, computing power and disk space are the two biggest cost concerns.
Advantages of Amazon EC2
The benefits of Amazon EC2 can be enormous in some situations. Here are a few of the immediate advantages:
- You don’t have to purchase or set up a virtual server; instead, you use Amazon’s hardware infrastructure. This is especially useful if you don’t have an IT person on staff, or if you don’t have the money to purchase a virtual server. As you will see later in this lesson, it’s relatively painless to set up your own virtual machine on Amazon EC2.
- You can easily obtain a machine to prototype or test a new application. If your organization is in a financial crunch, all of your machines may be in use or out of date, making it difficult to try new things. With Amazon EC2 you can obtain a machine for a few days or weeks for a relatively low cost, in order to test or learn new software and applications. In essence, this is what you’ll do in this course, as you use Amazon EC2 for just a few weeks so you can learn ArcGIS Server.
- You can easily obtain a server that is public-facing (in other words, that can be accessed by anyone on the Internet). In some organizations it takes a fair amount of paperwork, official approval, and coordination with IT staff to get a public-facing server. This is for good reason, since any time you open up a server to the world, there are a lot more security risks that come into play. Setting up a public-facing server on Amazon EC2 carries somewhat less risk because the machine is not running on your organization’s hardware and can be completely isolated from your network if you choose.
- You can add “auto scaling” rules that add or remove machines depending on how busy your site is at any given time. This is how Amazon EC2 gains the “Elastic” part of its name. This elasticity can be incredibly cost-efficient for certain types of sites, such as those responding to natural disasters. Suppose that you administer a weather site, and one afternoon a string of serious tornados hits. Your site will see a lot more traffic that day, especially if your site gets linked to by other sites. If you were hosting your site on premises you might run out of hardware, or it might take some time to add new machines. If you were hosting your site on Amazon EC2 with auto scaling rules, your site could temporarily expand to use whatever amount of hardware was needed.
EC2 instances and AMIs
Before going forward, there are two important vocabulary terms that you should understand regarding Amazon EC2:
- EC2 instance – An EC2 instance is a virtual machine running on Amazon EC2.
- AMI – An Amazon Machine Image (AMI, sometimes pronounced “ah-mee” or "Amy") determines the files, settings, and software that are applied when you create a new EC2 instance. You can think of an AMI as a blueprint for creating an EC2 instance. Also, when you work with an EC2 instance, you can save a “snapshot” of your work at any time by creating an AMI. This way, if something ever happens to your instance, you can create a new instance and continue where you left off.
How do you get software like ArcGIS Server running on Amazon EC2?
Esri has created an AMI that has ArcGIS Server installed and configured. You will use these AMIs to create EC2 instances, thereby getting the server software running on Amazon EC2. Once you get the instance running, you can log into it using an application called Windows Remote Desktop. This is the same way that you would remotely log in to any other computer in your network, except this time the machine is outside your network, running on Amazon EC2.
You can perform all of these steps on your own home computer as long as it has an Internet connection. In fact, it's recommended that you use your home computer because some workplace IT departments have placed restrictions on accessing computers outside the firewall (like Amazon EC2 instances) using Remote Desktop. Please note that you cannot use a personal hotspot through a mobile phone to log in to your EC2 instances.