Amazon's Elastic Cloud Compute (EC2) service experienced a prolonged outage that started on Thursday morning and stretched over the weekend. The problem was limited to Amazon's data center in the Northern Virginia area, and appears to be largely resolved at the time of my writing this news report.

Beyond the chorus of "I told you so" from opponents of cloud computing are some voices that highlight problems specific to Amazon's EC2. One point of contention is related to the lack of communication as Amazon worked to restore system availability. While the Service Health Dashboard accurately reflected the state of its various data centers around the world, some have complained that the updates were too vague and provided no background information whatsoever.

Another major criticism pertains to how the outage spanned more than one "availability zone." Amazon operates its cloud computing service across multiple data centers spanning different geographic regions, with each location containing multiple availability zones. Failures in one zone are supposed to be insulated from failures in another zone; the recent outage saw multiple zones go dark at the same time, however.

Without Amazon releasing additional details about how the zones are interrelated, customers will find it difficult to build effective safeguards into their applications to ensure high availability. Interestingly, Amazon's SLA provides for 99.95 percent availability for each region, but not for each availability zone, observed Network World.  For now, a new report from Computerworld noted that Amazon is still "digging deeply into the root causes of this event" and will reveal their findings in a post mortem.   

For more on this story:
- check out this article at Network World
- check out this article at The Register
- check out this article at Computerworld
- check out this article at TechNewsWorld

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