Cracking the cloud: An Amazon Web Services primer

Via ars technica

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It's nice to imagine the cloud as an idyllic server room—with faux grass, no less!—but there's actually far more going on than you'd think.

Maybe you're a Dropbox devotee. Or perhaps you really like streaming Sherlock on Netflix. For that, you can thank the cloud.

In fact, it's safe to say that Amazon Web Services (AWS) has become synonymous with cloud computing; it's the platform on which some of the Internet's most popular sites and services are built. But just as cloud computing is used as a simplistic catchall term for a variety of online services, the same can be said for AWS—there's a lot more going on behind the scenes than you might think.

If you've ever wanted to drop terms like EC2 and S3 into casual conversation (and really, who doesn't?) we're going to demystify the most important parts of AWS and show you how Amazon's cloud really works.

Elastic Cloud Compute (EC2)

Think of EC2 as the computational brain behind an online application or service. EC2 is made up of myriad instances, which is really just Amazon's way of saying virtual machines. Each server can run multiple instances at a time, in either Linux or Windows configurations, and developers can harness multiple instances—hundreds, even thousands—to handle computational tasks of varying degrees. This is what the elastic in Elastic Cloud Compute refers to; EC2 will scale based on a user's unique needs.

Instances can be configured as either Windows machines, or with various flavors of Linux. Again, each instance comes in different sizes, depending on a developer's needs. Micro instances, for example, only come with 613 MB of RAM, while Extra Large instances can go up to 15GB. There are also other configurations for various CPU or GPU processing needs.

Finally, EC2 instances can be deployed across multiple regions—which is really just a fancy way of referring to the geographic location of Amazon's data centers. Multiple instances can be deployed within the same region (on separate blocks of infrastructure called availability zones, such as US East-1, US East-2, etc.), or across more than one region if increased redundancy and reduced latency is desired

Elastic Load Balance (ELB)

Another reason why a developer might deploy EC2 instances across multiple availability zones and regions is for the purpose of load balancing. Netflix, for example, uses a number of EC2 instances across multiple geographic location. If there was a problem with Amazon's US East center, for example, users would hopefully be able to connect to Netflix via the service's US West instances instead.

But what if there is no problem, and a higher number of users are connecting via instances on the East Coast than on the West? Or what if something goes wrong with a particular instance in a given availability zone? Amazon's Elastic Load Balance allows developers to create multiple EC2 instances and set rules that allow traffic to be distributed between them. That way, no one instance is needlessly burdened while others idle—and when combined with the ability for EC2 to scale, more instances can also be added for balance where required.

Elastic Block Storage (EBS)

Think of EBS as a hard drive in your computer—it's where an EC2 instance stores persistent files and applications that can be accessed again over time. An EBS volume can only be attached to one EC2 instance at a time, but multiple volumes can be attached to the same instance. An EBS volume can range from 1GB to 1TB in size, but must be located in the same availability zone as the instance you'd like to attach to.

Because EC2 instances by default don't include a great deal of local storage, it's possible to boot from an EBS volume instead. That way, when you shut down an EC2 instance and want to re-launch it at a later date, it's not just files and application data that persist, but the operating system itself.

Simple Storage Service (S3)

Unlike EBS volumes, which are used to store operating system and application data for use with an EC2 instance, Amazon's Simple Storage Service is where publicly facing data is usually stored instead. In other words, when you upload a new profile picture to Twitter, it's not being stored on an EBS volume, but with S3.

S3 is often used for static content, such as videos, images or music, though virtually anything can be uploaded and stored. Files uploaded to S3 are referred to as objects, which are then stored in buckets. As with EC2, S3 storage is scalable, which means that the only limit on storage is the amount of money you have to pay for it.

Buckets are also stored in regions, and within that region “are redundantly stored on multiple devices across multiple facilities.” However, this can cause latency issues if a user in Europe is trying to access files stored in a bucket within the US West region, for example. As a result, Amazon also offers a service called CloudFront, which allows objects to be mirrored across other regions.

While these are the core features that make up Amazon Web Services, this is far from a comprehensive list. For example, on the AWS landing page alone, you'll find things such as DynamoDB, Route53, Elastic Beanstalk, and other features that would take much longer to detail here.

However, if you've ever been confused about how the basics of AWS work—specifically, how computational data and storage is provisioned and scaled—we hope this gives you a better sense of how Amazon's brand of cloud works.

Correction: Initially, we confused regions in AWS with availability zones. As Mhj.work explains in the comments of this article, "availability Zones are actually "discrete" blocks of infrastructure ... at a single geographical location, whereas the geographical units are called Regions. So for example, EU-West is the Region, whilst EU-West-1, EU-West-2, and EU-West-3 are Availability Zones in that Region." We have updated the text to make this point clearer.