Analogy

• When an electric appliance needs power, we plug it in into socket
• Electricity is readily available in our home but actuall generated over power stations
• We pay the electricity bill for whatever we have used bcoz electricity is metered
• If we apply the same analogy to software/information technology services, this is what cloud exactly does.

Pictorial Representation

Experiment: We are starting a new project for airline reservations

• Sample architecture will be as shown below

• Number of Server required to run this architecture at a bare minimum are 5

  • Availability Checker
  • Booking Server
  • Ticket Generator
  • Database
  • Gateway

• Where will these servers be located physically?

  • On-Premise Datacenter

• What will you do if Database crashed?

  • If the database is crashed whole application will be down
  • To resolve this, we will add a secondary database which has data in sync with primary database
  • Now even if primary db fails we can still run the show with secodary db

• What will happen if your datacenter has caught fire ?

  • This is Disaster and we need to have disaster recovery plan
  • Lets go with two datacenters in two locations of our enterprise
  • Pros: Effective for Disaster
  • Cons: Costly and requires decent connectivity between two sites
  • Lets go with only storing the backup in other site
  • Pros: Easy to implement
  • Cons: In Case of disaster, this approach takes lot of time to bring back application online

• What will happen if the users to your application grow rapidly only during holiday season.