Today, i am going to write another great thing about the cloud which is availability zones.
One of the great things about the cloud is the ability to be available at all times. Customers can today, build highly available applications using availability sets and virtual machines scale sets and they can also protect their applications and data from disasters through taking advantage of Geo-redundant storage with the GRS offering, and Azure Site Recovery by replicating their data and stateful VMs across different regions.
Availability zones offers it another capability for customers to build highly available applications within a region. The benefit that availability`s own software says that it protects customer`s applications and data within a region from data center level failures
So, the underlying database, if there is a problem this protects them from that issue.
Availability zones are fault isolated locations within an Azure region and each availability zones consists of one or more data centers. With each of them having independent power network and cooling.
For an example, one of the zones goes down because of a flood taking down one part of the city,If the customers have deployed their applications by replicating across three zones within the region, their applications will not see or experience any downtime and their business continuity is not going to get impacted within a region.
With availability zones, what is going to happen is that you think of three different data centers wherein customers deployed operations are distributed. However, one of the key value propositions is to have availability zones is not only for enabling high availability, but it also enables low latency replication for customers. It`s low latency because it is within the same zone/region.
So, you have geography where in we have two regions, let`s take, for an example, North Europe and West Europe. They are part of Europe region for us. So, these two are in two different cities in Europe. So, if we add availability zones within West Europe, wherein you are going to have three different availability zones in West Europe. So, the hierarchy is geography, region and availability zones. And within that availability zones which is not explicitly exposed for the customers as the data center and the racks and the nodes etc.
So, while creating VMs, what we try to make sure with availability zones is the workflow that the customers have to follow with the VM portal or Powershell or CMDLine interface. All of them are consistent. It`s just that an additional parameter called an availability zones that need to be chosen by the customer. So, they can pin their particular virtual machine in that particular zone.
It`s an optional parameter.
There is hierarchy of fault tolerance. Availability sets protects from hardware level failures and software level update failures. While availability zones protects them at data center level failures and software level update failures.
This is a very basic scenario, where i am writing about creating a single VM.
If you think about an enterprise grade application, and protecting that application from disaster demands and being sure they are highly available. You would want to distribute your VMs and the applications that are running on top of it across multiple zones. So, making it all of them simple through Cross Zone Virtual Machine scale sets.
The scale sets wherein you can homogeneous set of VMs that you create within a region. With Cross Zones Virtual Machine scale sets you can pick a region and specify the zone in which you want to have the virtual machines that are there within the scale sets. It automatically distribute across the zones. And here, have the flexibility for the customers to customize it. If they want to put it across two zones,they can do it. If they want to put it across two zones, they can do it. If they want to put it across three zones, they can do it. They could just put it across all of them in one zone, but they are not going to get the benefit of high availability capability from availability zones softwares, if you are able to put everything in.