Azure rebooted the server. The bank never noticed.

Frequently asked questions

What is an Azure update domain?

A group of VMs that Azure reboots together during planned maintenance. An availability set spreads VMs across multiple update domains, so maintenance takes them down one group at a time rather than all at once.

What's the difference between an update domain and a fault domain?

A fault domain groups VMs by shared hardware — the same rack, power and network switch, which fail together unplanned. An update domain groups VMs by planned-maintenance timing. They protect against different kinds of interruption.

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