Cloudyn points out AWS billing surprise

In a blog post, cloud monitoring service Cloudyn points out one way Amazon Web Services makes it tough for certain users to track spending.

Zev Schonberg writes that one of his customers found a nearly $20,000 discrepancy between Cloudyn's estimate of the customer's AWS usage for the month and the bill from AWS. Cloudyn's estimate was the cheaper of the two.

Schonberg did some digging and found that AWS charges users of Heavy Utilization Reserved Instances at the beginning of the month. It can do that because unlike most AWS services, customers must pay for their Heavy Utilization Reserved Instances even if they don't use the instance. It's spelled out on AWS' pricing page.

surprise_0.jpgSource: Greencolander via Flickr

Heavy Utilization Reserved Instances are useful to people who know for sure they'll use it. In that case, they can save quite a lot by reserving the instances.

Used or unused, however, AWS appears to charge for Heavy Utilization Reserved Instances on the first day of the billing period.

That can create problems for customers who are trying to closely monitor their spend. "Costs that are only fully incurred by the end of the month already appear on the first day, creating a spike that doesn’t really exist. This kind of noise makes it difficult to practice IT change management in a meaningful way," Schonberg wrote. "These artificial spikes can confuse users who then become jaded and ignore anomalies that really do represent a serious breach of usage or spending."

It's hard to guess how many people this scenario impacts. But it's one spot where AWS could make a change to help customers that are increasingly eager to monitor their cloud spend.

I wouldn't be surprised if it does. The company seems to be aware of monitoring and automation needs of customers; it recently added a new automation feature that lets users shut down unused EC2 instances.

Read more of Nancy Gohring's "To the Cloud" blog and follow the latest IT news at ITworld. Follow Nancy on Twitter at @ngohring. For the latest IT news, analysis and how-tos, follow ITworld on Twitter and Facebook.

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