Amazon's Elastic Compute Cloud (EC2) service has been gaining both features and followers in the two years since its inception. EC2 started out as a virtualized hosting platform. In an 2006 interview with Artima, Amazon's Jeff Barr noted that:

I like to think of it as hardware as a service. We have a processing grid of many, many servers... and we give developers a way to actually rent time on those servers by the wall clock hour. To do that we use a virtualization technology called XEN...

The first step a developer does is create something called an AMI, an Amazon Machine Image. Inside that image, you configure your local database, your local applications, whatever local services you need to have running on that machine... You then store those images inside of S3 [Amazon's Simple Storage Service], and then, using Web services, or using a control panel, you can start up as many instances of these machine images as they would like...

Amazon has since added many features to EC2 that make it an ideal environment for highly reliable, fault-tolerant applications. The latest such features are "elastic IP address" and "availability zones." In a recent blog post, On the Road to Highly Available EC2 Applications, Amazon CTO Werner Vogels describes these features as follows:

• Elastic IP addresses are associated with a customer account and allow the customer to do its own dynamic mapping of IP address to [virtual server] instance. Using this dynamic mapping applications can remain reachable even in the presence of failures. This is an area where for example DNS reconfiguration is too slow a technique.
• Availability Zones allow the customer to specify in which location to launch a new EC2 instance. The world is divided up into Regions and a Region can hold multiple Availability Zones. These Zones are distinct locations within a region that are engineered to be insulated from failures in other Availability Zones and provide inexpensive, low latency network connectivity to other Availability Zones in the same region. By launching instances in separate Availability Zones, applications can be protected from failure of a single location.

What do you think of Amazon's EC2 as a hosting environment for high availability applications?