AWS makes auto-recovery the default for EC2 instances

Your cloudy server will not self-destruct – even if the hardware it runs on does

Amazon Web Services has added a small but important resilience feature: instances in its Elastic Computing Cloud (EC2) now include automatic recovery by default.

EC2 instances could previously be set to recover automatically by setting an alarm in Amazon CloudWatch – AWS's monitoring and observability service.

But AWS has switched recovery on by default in EC2 instances.

AWS states that if an underlying hardware problem comes along, EC2 instances will therefore find themselves a new home in the Amazonian cloud – complete with its instance ID, private IP addresses, public IPv4 IP address, Elastic IP addresses, and all instance metadata. Data in memory is, however, lost.

AWS's brief announcement of the new feature and other documentation makes no mention of recovery points for data on disks, nor the time required for an auto-recovered server to resume operations.

It's still possible to disable the auto-recovery feature. That may sound like an odd choice to make, but AWS's documentation offers one reason to consider it: instances in placement groups (an AWS feature that lets you ensure instances run a particular group of hardware) are restored to the same placement group. Hardware faults in a server could easily be an indication of a problem in a rack or row, so perhaps auto-recovery into an unstable environment is a less attractive option than auto-recovery into another availability zone or region.

AWS recommends working across multiple availability zones for the sake of resilience, while failures in big regions like the venerable US-EAST-1 served notice that building for resilience across multiple regions is also entirely sensible. ®

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