Limits

• Every server will have limited Hardware resources, these resource can cater only certain limit
• Example Scenario:
  • Our each Server component like availability checker can respond to 5000 parallel users/requests. But right now we have 10000 users
• Solution for the above scenario is Scaling. Scaling is of two types
  • Vertical:
    • Increase hardware resources of the current server
  • Horizontal:
    • Increase number of servers doing the same job
• One unsolved puzzle over here is what will we do if the traffic comes down to 3000 users. We need a way to scale out/scale up (increase) and scale in/scale down (decrease) the number of servers based on demand
• In all the cloud, the scale in and scale out is supported and also referred as elasticity.

Terms So far

• Availability:
  • A measure of system uptime.
  • If your system is up for almost all the time it is considered to be Highly Available.
• Fault Tolerance:
  • Capability of system to recover from failures/faults
• Elasticity:
  • Capability of System to Scale up or down depending on need of the user is considered as elasticity

Virtualization

• Allows to create multiple simulated environments or dedicated resources from single physical hardware system.

Understanding virtualization

• To run applications we follow the above workflow

• When the applications dont use your hardware resources to the maximum potential, ROI (Return on Investment) is very low

• Rather than using one operating system on the physical server, we can create multiple vms on the same physical server. This kind of virtualization is called as Server Virtualization

• Every VM gets

  • Virtual disk
  • is connected to virtual network using virtual socket
  • a CPU and memory (virtual)
  • Has some Opertaing system

• Server virtualization is supported by Softwares like VMWare ESxi

• All the clouds use Server Virtualization for creating virtual machines

  • Amazon calls it as EC2
  • Azure calls it as Azure VM