How does the Hyper-V parent partition architecture work?

Microsoft's hypervisor relies on several modules and services to deploy and manage virtual machines. Do you know what they are and how they work?

There are several modules that operate together to build the Microsoft Hyper-V hypervisor concept. Hyper-V implements a main partition called the parent partition, which runs Hyper-V's main service called Virtual Machine Management Service. VMMS is the main module designed to control all aspects of Hyper-V server virtualization, but also uses several sub-modules as explained below.

WMI Provider: This module acts as an interface between developers and VMs running in the child partitions. The Windows Management Instrumentation (WMI) Provider component implements the necessary WMI classes for developers to execute an action on the VMs running on a Hyper-V host. Microsoft implements root\virtualization as the core WMI Provider that contains networking, VM BIOS, storage and video classes to help you interact with Hyper-V VMs.

Hyper-V VSS Writer: The backups that a Hyper-V application performs are handled by the Volume Shadow Copy Service (VSS) Writer component. The Hyper-V VSS Writer backs up VMs without any downtime. The Hyper-V VSS Writer and Hyper-V Volume Shadow Copy Requestor service running in a VM as part of Integration Services enable online backup functionality. Any requests coming for VM backups are handled by the Hyper-V VSS Writer and then sent to the Hyper-V Volume Shadow Copy Requestor service.

Virtual Machine, Worker Process and Snapshot Managers: The Virtual Machine Manager component is responsible for managing VM states. When you open the Hyper-V Manager, VMMS.exe calls the Virtual Machine Manager component to refresh VM statuses. Worker Process Manager launches a VM worker process for each VM and keeps track of all worker processes running in the parent partition. Worker Process Manager also processes snapshots or checkpoints for running VMs. On the other hand, Snapshot Manager – as the name suggests – handles snapshots or checkpoints for VMs that are offline.

Single Port Listener for RDP: Remote Desktop Protocol (RDP) is used by the Virtual Machine Connection Manager tool to connect to a VM over network port 2179. The VMMS.exe listens on network port 2179 for incoming RDP requests from the VMConnect.exe tool. When VMMS.exe receives a RDP request, it redirects the request to the Single Port Listener for RDP component, which in turn, helps to enable RDP of a VM.

Cluster Resource Control: With the help of Cluster Resource Control component, VMMS.exe enables high availability for VMs running in a Hyper-V cluster. Cluster Resource Control uses HVCLUSRES.DLL to interact with VM resources.

Courtesy: Nirmal Sharma