An Azure data center computers rack identifies with a fault domain.
Such a fault domain allocation is determined by Azure infrastructure at deployment time.
The service owner cannot control the allocation of a fault domain.
The service owner can programmatically detect the fault domain hosting a service.
An upgrade domain ensures an application is still available while being updated. This is achieved by upgrading one upgrade domain at a time.
The upgrade procedure for one upgrade domain is:
stop instances in upgrade domain
- upgrade application
- bring the instances back online