• VMSS allows you to scale VMs in and out based on certain rules (utilization or queue) / helps with [[202404071304 Resiliency Overview|resiliency]]
  • For example: if cpu utilization goes above 70% add 2 more VMs
  • max: 1000
• These are just [[202404161835 Azure VM Basics|Azure VM]]s so nothing special in that way. You can interact with them whichever way you want.
  • These are not special. Or should not be special. So if one has any issue, it should be able to get deleted and recreated.
• this scale set is kept behind a LB.
• There are two modes: flex and uniform. But use flex. Uniform is legacy.
  • Uniform means all vms of same size
    • for large scale stateless
  • Flex can include different sizes
• You can get termination notification
• You can look at the logs to see what has happened in the past
• When creating an [[202404161835 Azure VM Basics|Azure VM]] you can specify if you want to add it to an existing scale set.
• use [[202404171828 Azure Spot can help reduce prices for Azure VMs|Azure Spot can help reduce prices for Azure VMs]]
  • but vm can be removed at any time, so architect accordingly
  • policies:
    • deallocate - remove compute, but disks are saved
    • delete - delete everything
• upgrade policy
  • automatic
  • rolling - so any changes to image or profile is not done for the whole scale set in one go.
  • manual

Types of scaling

• scheduled
• automatic - based on metrics

some faqs

# create
az vmss create --resource-group myResourceGroup --name webServerScaleSet --image Ubuntu2204 --upgrade-policy-mode automatic --custom-data cloud-init.yaml --admin-username azureuser --generate-ssh-keys

# Scale
az vmss scale --name webServerScaleSet --resource-group MyResourceGroup --new-capacity 6

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references:

VMSS Overview