A fault domain is a physical server, if all machines are in a single fault domain, they can fail together. Different fault domains have independent power and network sources
An availability set is a group of different fault domain. Each new VM is deployed to a different fault domain
Update domains are different racks in an fault domain, they are restarted one at a time. It's good to have VMs distributed across update domains too
If two or more instances are deployed in same availability set, you get 99.95% SLA
It's recommended to use managed disks for Availability sets
The newly created VMs must be then assigned to a Availability Set
Assigning a VM to an Availability Set can only be done upon creation
When an Availability Set it deleted all its VMs are deleted as well
