Horizontal and Vertical Scaling

• Vertical Scaling is about increasing resources to current vm/physical machine (increasing RAM/CPU).
  • Adopting Vertical Scaling means we need to restart the workload which means downtime
  • Generally scaling is used in the sense of increasing but the situation is same even to decrease resource
• Horizontal scaling is about increasing workloads to distribute the load among mutliple systems
  • Adopting Horizontal scaling means we need not have a downtime because we are adding more workloads (vms)
    
• In Azure, We can perform both horizontal and vertical scaling

Vertical Scaling in Azure

• Changing the vm size in Azure is a way to perform vertical scaling, This leads to restart of the vm
• Create a VM with apache
• Now resize the VM size
  

Horizontal Scaling in Azure

• We have two options
  • Manually add/remove vms
  • Automatically increase or decrease vmss => Azure Virtual Machine Scale Set (VMSS)

Azure Virtual Machine Scale Sets (VMSS)

• Virtual Machine Scale Set Refer Here
• VMSS lets us do horizontal scaling, with
  • fixed count maintained
  • scale out and in based on some metric to automatically increase or decrease vms
• A VMSS represents a Virtual Machine with some component/application which needs to be scaled (order service, user service not both)
• To Create a VMSS ideally we need an Virtual machine Image rather than using userdata/custom data/run commands to install applications.
• Exploring options while creating VMSS