Amazon Elastic Compute Cloud is an IaaS platform offered through Amazon Web Services. It provides raw infrastructure for the deployment of pretty much whatever operating system your applications require. As such, Amazon EC2 provides control over the OS, but it lacks automated patching. That puts the onus on you to keep the OS up-to-date.
You can import supported virtual-machine images from your existing environment. (Amazon EC2 currently supports Windows Server 2003 R2 and Windows Server 2008 R1/R2 via images from VMware ESX VMDK, Citrix Xen VHD, or Microsoft Hyper-V VHD. The company plans to support more OSs and virtual platforms in the future.) Alternatively, you can create instances based on a variety of Linux and Windows OSs. Amazon EC2 also offers preconfigured instances with popular database servers (IBM DB2, MySQL, and more), resource management solutions, Web servers (Apache, IIS/ASP.NET), application development environments, application servers, and media servers.
The free usage tier offers the ability to create a “micro” Linux and Windows instance, along with other resources that your IT personnel can use to test and become familiar with Amazon EC2. The company has three purchasing models: On-Demand Instances, in which you pay an hourly rate with no commitment; Reserved Instances, in which you pay a one-time fee and a discounted hourly rate with a one- or three-year commitment; and Spot Instances, in which you bid on pricing. You can estimate your monthly bill using Amazon’s calculator, with prices varying based on the region in which your instance is running.
The company’s SLA states a 99.95 percent annual uptime, but you must run at least two copies of an instance in two separate “availability zones” to receive service credits.
Amazon Web Services also offers two database services: Amazon DynamoDB is a fully managed NoSQL database cloud service, provided under the free usage tier with limitations, while Amazon Relational Database Service provides a cloud-based relational database with capabilities similar to a MySQL or Oracle database.
Amazon Elastic Block Store offers block-level storage volumes for use with Amazon EC2 instances. Each instance you contract for includes some storage, but EBS provides for redundancy. You can format the storage volume as you would a hard drive, using your desired file system. You can also create point-in-time snapshots of volumes for backup purposes. Though you must pay for snapshot storage, these backups will require considerably less space than the original volumes, for several reasons: They’re compressed, empty blocks are not saved, and each snapshot after the first contains only new or modified data.
Rackspace Cloud Hosting
Rackspace’s Cloud Hosting service provides raw infrastructure with control over the OS. Automatic OS updates are included with the optional Managed Service Level. Unlike Amazon EC2 and most other IaaS providers, Rackspace doesn’t let you upload your own existing virtual machines; you must choose from the Windows and Linux versions the company supports.
Rackspace charges a per-hour fee for each server, with an assortment of server sizes. Unlike some other cloud hosts, Rackspace doesn't allow you to stop the per-hour charges by halting instances. If you want to keep an idled server without being charged for a given period of time, you must back up your image (incurring charges from Rackspace’s Cloud Files service), delete the server from your account, and then add it back when you want to run it later.
Use Rackspace’s calculator for a better estimate of your costs. Keep in mind that the company currently doesn’t offer a free trial, but you can freely create an account and access the administrative portal if you want to get a better idea of how the service works. You’ll be charged only if you create instances or utilize their other resources.
Rackspace’s Managed Service Level provides monitoring, OS and application infrastructure layer support (including automated updates and patches), and technical guidance on your cloud servers (visit the Rackspace website to see which Windows and Linux operating systems the company supports).
Rackspace’s SLA states that its data center network is available 100 percent of the time--excluding scheduled maintenance, defined as downtime announced at least ten business days in advance and not exceeding 60 minutes in a calendar month. As a result, the guaranteed availability percentage essentially equates to about 99.999 percent, which is the best out of the three cloud hosts I've reviewed here.
Rackspace doesn’t offer a separate cloud database service, but you can add Microsoft SQL Server 2008 R2 (Standard and Web editions) to select Windows servers. The company provides cloud storage through its Cloud Files service.
Choosing a Cloud Host
Determining which provider is best for your business depends largely on what you need the service for, how you wish to use it, and the degree of OS control you require for application development or hosting. You should also consider the provider's current security accreditations and evaluate the encryption options the company supports.
Windows Azure is a great cloud host for application developers who don’t need Linux (although Microsoft plans to add Linux support by year’s end). Windows Azure supports nearly all programming languages and is competitively priced. If your application allows you to use Microsoft’s operating systems, you won’t need to worry about OS patches or updates.
Amazon EC2 is a strong cloud host if you require full OS control of Windows or Linux machines, but can do without automated OS patching. Amazon Web Services also offers a range of other cloud services (more than Microsoft or Rackspace) that I didn’t cover here.
Rackspace is a good choice if you desire the OS control that an IaaS provider delivers, combined with the managed services that a PaaS provider affords. On the other hand, Rackspace lacks some of the features that the other two services have, which renders it the most expensive of the three cloud hosts here.
Here’s my take on how the three services score on key features or characteristics (on a scale of one to five; higher scores are better):
For more about cloud security, read "Into the Cloud--Securely."
Eric Geier is a freelance tech writer. He’s also the founder of NoWiresSecurity, which helps businesses protect their Wi-Fi with enterprise (802.1X) security, and On Spot Techs, which provides on-site computer services.