Virtual machine scale sets are a way to manage Azure VMs as a group. They provide easy deployment and management options, and simple ways to integrate with support for autoscale and load balancing. Patching thousands of VMs in scale sets is a critical management task that we recommend our customers to perform for the continued security, performance, and stability of the applications those VMs support. A new capability is in preview: automatic guest OS image updates in scale sets. After you enable this feature for your scale sets, when a new OS image is published with the latest features, security patches, and performance improvements, your scale sets and Azure Service Fabric clusters can receive these updates automatically, without your intervention. The new image will roll out to the VMs in your scale sets in batches based on preconfigured health probes to check for application issues. So your app can remain highly available even if there are incompatibilities between your app and the new OS image. You can monitor the status of upgrades programmatically or through an out-of-the-box experience in the Azure portal.