After VMSS and applications are deployed, they need to be actively maintained. Planned maintenance should be conducted periodically to ensure that both the environment and application is up to date with the latest features, and the environment is current from a security and resilience point of view.

Upgrades can be associated with applications, the guest VM instance, or the image itself. Upgrades can be quite complex because they should happen without affecting the availability, scalability, and performance of environments and applications. To ensure that updates can take place one instance at a time using rolling upgrade methods, it is important that VMSS supports and provides capabilities for these advanced scenarios.

There is a utility provided by the Azure team to manage updates for VMSS. It's a Python-based utility that can be downloaded from https://github.com/gbowerman/vmssdashboard. It makes REST API calls to Azure to manage scale sets. This utility can be used for starting, stopping, upgrading, and re-imaging VMs on a fault domain or group of VMs, as shown in the following screenshot: