What is a difference between the Availability Zones and Fault domains feature of the Availability Sets in Microsoft Azure?
I am working through the module Discuss core Azure architectural components. And there I met the description of the Fault domains:
Fault domains. Fault domains provide for the physical separation of your workload across different hardware in the datacenter. This includes power, cooling, and network hardware that supports the physical servers located in server racks. In the event the hardware that supports a server rack becomes unavailable, only that rack of servers would be affected by the outage.
Also, there is an explanation of some of the Availability Zones features:
Each availability zone is an isolation boundary containing one or more datacenters equipped with independent power, cooling, and networking.
If one availability zone goes down, the other continues working.
The availability zones are typically connected to each other through very fast, private fiber-optic networks.
Availability zones allow customers to run mission-critical applications with high availability and low-latency replication.
Availability zones are offered as a service within Azure, and to ensure resiliency, there’s a minimum of three separate zones in all enabled regions.
I really do not see the difference between both. Both concepts are about physical separation of datacenter pieces within a single datacenter. So, could someone point out what is the main point in having these two terms? Don't they mean the same things?
May I consider the matter as follows? First we have a region, which is a facility which contains a few (at least three) Availability Zones (AZ), then each AZ contains one or more datacenters, then each datacenter contains a few Availability Sets, and here we have that each Availability Set contains a few racks, and each of these racks represents a separate Fault domain.
I think the Availability Zone IS the datacenter, and you have multiple zones within a region. The fault domain can be thought of as WITHIN the datacenter (going by the description you included). The domains are further segregated as described below.
Regions and Availability Zones in Azure
"An Availability Zone in an Azure region is a combination of a fault domain and an update domain. For example, if you create three or more VMs across three zones in an Azure region, your VMs are effectively distributed across three fault domains and three update domains. The Azure platform recognizes this distribution across update domains to make sure that VMs in different zones are not scheduled to be updated at the same time."