Azure is rebooting your server. Nobody notices.

Frequently asked questions

Why can't a single VM survive Azure's own maintenance?

Azure periodically reboots the physical host underneath a VM for planned maintenance — a single VM has no way to stay up through that, no matter how well the application itself is built.

What does an availability set actually do?

It spreads your VMs across separate fault domains (different racks and power) and update domains (different maintenance groups), so planned maintenance or a hardware fault takes out one VM at a time while the load balancer's health probe keeps sending traffic to the ones still up.

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