VMSS allows for the creation of up to 1,000 VMs in a scale set when using a platform images and 100 VMs if using a custom image. If the number of VMs is less than 100 in a scale set, they are placed in a single availability set; however, if they are greater than 100, multiple availability sets are created, known as placement groups, and VMs are distributed among these availability sets. We know from the last chapter that VMs in an availability set are placed on separate fault and update domains. Availability sets related to VMSS have five fault and update domains by default. VMSS provides a model that holds metadata information for the entire set. Changing this model and applying changes impacts all VM instances. This information includes maximum and minimum VM instances, the operating system SKU and version, the current number of VMs, fault and update domains, and more.  This is demonstrated in the following diagram: