Let's go through some important points when it comes the topics discussed in this section
This refers to technologies that can be used to minimize IT disruptions by ensuring applications and infrastructure is made fault-tolerant.
Let's say that you had the following architecture for your application. Your application is hosted on a single virtual machine.
What happens if the virtual machine goes down for any reason, your application would not be available.
To make your application more redundant and more tolerant to failures, why not host your application on a collection of servers
Here even if one machine were to go down , you would still have the other one available. This makes your application more tolerant to infrastructure level failures.
You can also increase the availability for your virtual machines by distributing them across Availability Zones or Availability Sets.
This refers to the concept of minimizing IT disruptions by recovering them to another data center that could be located hundreds to miles away from the original data center hosting your application.
The following architecture diagram is an example of implementing disaster recovery
Here your application is running on virtual machines in the West US region. Here the users are accessing your application.
At the same time, you might have the application hosted in another region (East US). The application might be in a shutdown state. This is only meant to be running if the primary region goes down for any reason.
Not lets say there is a disaster in the West US region and all the data centers go down.
To minimize any disruption to your users , the requests to the application could now be redirected to the application in the East US region. So now you would start the application here and make sure all requests are routed to the secondary region.
Elasticity refers to the concept of how flexible your architecture can scale based on demand.
For virtual machines , you can increase or decrease the size of the virtual machine at any point in time.
The different cloud service models
Infrastructure as a service (IaaS)
An example is the Azure virtual machine service.
Here you dont need to manage the underlying infrastructure.
The physical servers and storage is managed for you.
This helps remove the capital expense and reduces ongoing cost.
The Virtual Machine also has an SLA. To achieve that SLA for any on-premise server would require a lot of work.
Infrastructure cloud services also allow you to scale based on demand.
Platform as a service
An example is the Azure SQL Database service or the Azure Web App service.
Here you dont need to manage the infrastructure or even the underlying operating system and platform components.
You can just start hosting your data or your web application.
Reduces development time.
You can use an array of database technologies available in the case of Azure.
All of these services use a Pay-as-you-go model.
Software as a service
An example is Microsoft Office 365.
Here you dont need to manage the infrastructure or even the underlying operating system, platform components or even the software.
Here you just start directly using the software.
You can access your application data from anywhere.
You dont have the headache of managing anything.
Public Cloud
These are services that are offered over the public internet.
Its available to anybody who wants to use them. Users then pay based on service they use.
Here all the servers and storage is managed by the cloud provider
Advantages of the Public Cloud
No need for a capital investment You normally dont pay any money upfront to use a cloud service. Most of the services are based on a pay-as-you-go model.
You dont need to manage the underlying physical infrastructure. Hence on-going maintenance costs are also reduced.
Cloud providers such as Azure have data centers located at different regions across the world.
You can quickly provision resources on the cloud. It allows you to get up and running in no time.
Private Cloud
These are set of services that are normally only used by users of a business or organization.
The private cloud could be hosted either on the companys on-premise environment. Or it could be provided by a third-party service provider.
Advantages of the Private Cloud
The business has complete control over the environment.
They can implement their own security protocols at every layer to secure the environment.
The data held in the environment is in complete control by the business.
Hybrid Cloud
This is a combination of both the public and private cloud.
It allows data and applications to be shared across both cloud environments.
Advantages of the Hybrid Cloud
Businesses can still leverage their existing on-premise environment. This is important if they have already made a substantial investment in getting their environment in place.
They can keep data which needs to be secured by their standards in their on-premise environment.
They can extend their infrastructure to the cloud without making a further investment.
They can move workloads to the cloud gradually.