Micro Instances offer a small amount of consistent CPU resources that let users burst CPU capacity when additional cycles are available, Amazon said.
"I can't tell you how many of you have told me you'd like to run smaller applications at lower cost on EC2," Jeff Barr, AWS evangelist, wrote in a blog post. "These applications are typically low traffic/low throughput – web applications, web site hosting, various types of periodic cron jobs and the like. I'm happy to say we have now built an instance type exactly for these purposes."
Micro Instances, Barr wrote, let users run smaller applications starting at 2 cents per hour for Linux/Unix applications and 3 cents per hour for Windows. AWS has launched Micro Instances in all regions and users can buy Reserved Micro Instances or Micro Instances can be purchased on the Spot Market. Reserved Micro Instances let users make a one-time payment to reserve an instance, which results in an hourly discount on using that instance. For Micro Instances on the Spot Market, prices can vary based on market conditions.
They come in both 32-bit and 64-bit varieties and have 613 MB of RAM. Barr cautioned, however, that Micro Instances have no local, ephemeral storage, so users will need to Boot from EBS. Instances can be tracked with Amazon's CloudWatch utility, and if CPU utilization nears 100 percent, users can add more Micro Instances or jump to a larger instance type, Barr wrote.
Amazon said Micro Instances are designed mostly to host Web applications and sites that receive tens of requests per minute, but that they can also be used for DNS services, load balancers, proxies and similar services that handle a low volume of requests; lightweight cron-driven tasks like monitoring, health checks or data updates; and hands-on training and other classroom use.
Gartner Research Director Lydia Leong, however, said Micro Instances are best suited for low-traffic enterprise apps and could be a low-cost first step toward moving to the cloud.
"Amazon has suggested that Micro Instances can be used for small tasks - monitoring, cron jobs, DNS, and other such things," wrote Leong in an analysis of Micro Instances on EC2. "To me, though, smaller instances are perfect for a lot of enterprise applications. Tons of enterprise apps are 'paperwork apps' - fill in a form, kick off some process, be able to report on it later. They get very little traffic, and consolidating the myriad tertiary low-volume applications is one of the things that often drives the most attractive virtualization consolidation ratios…. I read micro instances as being part of Amazon’s play towards being more attractive to the enterprise, since tiny tertiary apps are a major use case for initial migration to the cloud. Smaller instances are also potentially attractive to the test/dev use case, though somewhat less so, since more speed can mean more efficient developers (fewer compiling excuses)."
Leong added that Micro Instances are priced to help Amazon better compete against its cloud computing rivals. For example, Micro Instances are price-competitive with the low end of Rackspace Cloud Servers, which are 1.5 cents per hour for 256 MB and 3 cents per hour for 512 MB of RAM. It also gives Amazon more ammo to compete with the likes of Terremark and VirtuStream, Leong added.
"So Amazon's by no means alone in this segment – but it's a positive move that rounds out their cloud offerings," she wrote.