Fault domain

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.

Upgrade domain

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