Using Amazon Web Services

Working with the Elastic Compute Cloud (EC2)

Amazon Elastic Compute Cloud (EC2) is a virtual server platform that allows users to create and run virtual machines on Amazon's server farm. With EC2, you can launch and run server instances called Amazon Machine Images (AMIs) running different operating systems such as Red Hat Linux and Windows on servers that have different performance profiles. You can add or subtract virtual servers elastically as needed; cluster, replicate, and load balance servers; and locate your different servers in different data centers or “zones” throughout the world to provide fault tolerance. The term elastic refers to the ability to size your capacity quickly as needed.

The difference between an instance and a machine image is that an instance is the emulation of a hardware platform such as X86, IA64, and so on running on the Xen hypervisor. A machine image is the software and operating system running on top of the instance. A machine image may be thought of as the contents of a boot drive, something that you could package up with a program such as Ghost, Acronis, or TrueImage to create a single file containing the exact contents of a volume. A machine image should be composed of a hardened operating system with as few features and capabilities as possible and locked down as much as possible.

The pricing of these different AMI types depends on the operating system used, which data center the AMI is located in (you can select its location), and the amount of time that the AMI runs. Rates are quoted based on an hourly rate. Additional charges are applied for:
• the amount of data transferred
• whether Elastic IP Addresses are assigned
• your virtual private server's use of Amazon Elastic Block Storage (EBS)
• whether you use Elastic Load Balancing for two or more servers
• other features

System images and software

You can choose to use a template AMI system image with the operating system of your choice or create your own system image that contains your custom applications, code libraries, settings, and data. Security can be set through passwords, Kerberos tickets, or certificates.

These operating systems are offered:
• Red Hat Enterprise Linux
• OpenSuse Linux
• Ubuntu Linux
• Sun OpenSolaris
• Fedora
• Gentoo Linux
• Oracle Enterprise Linux
• Windows Server 2003/2008 32-bit and 64-bit up to Data Center Edition
• Debian

Most of the system image templates that Amazon AWS offers are based on Red Hat Linux, Windows Server, Oracle Enterprise Linux, and OpenSolaris. When you create a virtual private server, you can use the Elastic IP Address feature to create what amounts to a static IP v4 address to your server. This address can be mapped to any of your AMIs and is associated with your AWS account. You retain this IP address until you specifically release it from your AWS account. Should a machine instance fail, you can map your Elastic IP Address to fail over to a different AMI. You don't need to wait until a DNS server updates the IP record assignment, and you can use a form to configure the reverse DNS record of the Elastic IP address change.

 

Working with Amazon Storage Systems

When you create an Amazon Machine Instance you provision it with a certain amount of storage. That storage is temporal, it only exists for as long as your instance is running. All of the data contained in that storage is lost when the instance is suspended or terminated, as the storage is reassigned to the pool for other AWS users to use. For this and other reasons you need to have access to persistent storage. The Amazon Simple Storage System provides block storage, but is set up in a way that is somewhat unique from other storage systems you may have worked with in the past.

Amazon Simple Storage System (S3)

Amazon S3's cloud-based storage system allows you to store data objects ranging in size from 1 byte up to 5GB in a flat namespace. In S3, storage containers are referred to as buckets, and buckets serve the function of a directory, although there is no object hierarchy to a bucket, and you save objects and not files to it. It is important that you do not associate the concept of a filesystem with S3, because files are not supported; only objects are stored. Additionally, you do not “mount” a bucket as you do a filesystem.

The S3 system allows you to assign a name to a bucket, but that name must be unique in the S3 namespace across all AWS customers. Access to an S3 bucket is through the S3 Web API (either with SOAP or REST) and is slow relative to a real-world disk storage system. S3's performance limits its use to non-operational functions such as data archiving and retrieval or disk backup. The REST API is preferred to the SOAP API, because it is easier to work with large binary objects with REST.

The S3 service is used by many people as the third level backup component in a 3-2-1 backup strategy. That is, you have your original data (1), a copy of your data (2), and an off-site copy of your data (3); the latter of these may be S3.

Note: Keep in mind that while Amazon S3 is highly reliable, it is not highly available. You can definitely get your data back from S3 at some point with guaranteed 100% fidelity, but the service is not always connected and experiences service outages. 

Amazon Elastic Block Store (EBS)

The third of Amazon's data storage systems are devoted to Amazon Elastic Block Storage (EBS), which is a persistent storage service with a high operational performance. Advantages of EBS are that it can store file system information and its performance is higher and much more reliable than Amazon S3. That makes EBS valuable as an operational data storage medium for AWS. The cost of creating an EBS volume is also greater than creating a similarly sized S3 bucket.

CloudFront

Amazon CloudFront is referred to as a content delivery network (CDN), and sometimes called edge computing. In edge computing, content is pushed out geographically so the data is more readily available to network clients and has a lower latency when requested. You enable CloudFront through a selection in the AWS Management Console.

You can think of a CDN as a distributed caching system. CloudFront servers are located throughout the world—in Europe, Asia, and the United States. As such, CloudFront represents yet another level of Amazon cloud storage. A user requesting data from a CloudFront site is referred to the nearest geographical location. CloudFront supports “geo-caching” data by performing static data transfers and streaming content from one CloudFront location to another.

Understanding Amazon Database Services

Amazon offers two different types of database services: Amazon SimpleDB, which is non-relational, and Amazon Relational Database Service (Amazon RDS).

Amazon SimpleDB

Amazon SimpleDB is an attempt to create a high performance data store with many database features but without the overhead. To create a high performance “simple” database, the data store created is flat; that is, it is non-relational and joins are not supported. Data stored in SimpleDB domains doesn't require maintenances of a schema and is therefore easily scalable and highly available because replication is built into the system. Data is stored as collections of items with attribute-value pairs, and the system is akin to using the database function within a spreadsheet.

Amazon Relational Database Service (RDS)

Amazon Relational Database Service is a variant of the MySQL5.1 database system, but one that is somewhat simplified. The purpose of RDS is to allow database applications that already exist to be ported to RDS and placed in an environment that is relatively automated and easy to use. RDS automatically performs functions such as backups and is deployable throughout AWS zones using the AWS infrastructure.

In RDS, you start by launching a database instance in the AWS Management Console and assigning the DB Instance class and size of the data store. Any database tool that works with MySQL 5.1 will work with RDS. Additionally, you can monitor your database usage as part of Amazon CloudWatch.

Choosing a database for AWS

In choosing a database solution for your AWS solutions, consider the following factors in making your selection:
• Choose SimpleDB when index and query functions do not require relational database support.
• Use SimpleDB for the lowest administrative overhead.
• Select SimpleDB if you want a solution that autoscales on demand.
• Choose SimpleDB for a solution that has a very high availability.
• Use RDS when you have an existing MySQL database that could be ported and you want to
minimize the amount of infrastructure and administrative management required.
• Use RDS when your database queries require relation between data objects.