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Hyper-V Integration Services provides a set of components that help improve VM performance. Integration Services provides two types of components: drivers and services. The drivers play an important role in enhancing VM performance and the services do a specific job. For example, the VMBus driver acts as a communication channel to improve communication between VMs and the parent partition.
There are five services installed in a VM as part of the Hyper-V Integration Services and each plays a role in enabling a specific function. The services include operating system shutdown, time synchronization, data exchange, heartbeat and backup (volume checkpoint). Windows Server 2012 R2 added one more service called guest services, which enables the copying of files to the VM.
There are three main sets of drivers included in Hyper-V Integration Services that work together to enhance the performance of VMs: Virtualization Service Provider (VSP), Virtualization Service Client (VSC) and VMBus drivers. The VSP driver runs on the parent partition and the VSC driver runs on the child partition. There are four VSPs running in the parent partition and four corresponding VSCs running in the child partition. VSCs communicate with the VSPs running in the parent partition. For example, if a VM requires network services, it uses its VSC network driver to communicate with the VSP network driver running in the parent partition.
It is important to note that VSC and VSP cannot communicate directly; they need to use a medium for communication. That’s where the VMBus driver comes into play. The VMBus driver runs in both the parent and child partitions and facilitates communication between VSPs and VSCs. The VMBus running in the child partition communicates with the VMBus running in the parent partition, which operates in the host kernel space. Since the kernel space has direct access to the hardware, the VSC communications with VSP never suffer from performance loss.
To make sure the VMBus driver is installed and enabled on the Hyper-V host and VMs, launch Device Manager, then expand System Devices and check “Microsoft Virtual Machine Bus Provider.”
To ensure VSCs are installed properly in the VM as part of the Hyper-V Integration Services, go to Device Manager of the VM operating system and check the VSCs by expanding the appropriate nodes as shown in the screenshot taken from a VM running on the Hyper-V host:
By default, Microsoft implements VMBus and VSP design in the hypervisor (parent partition). In other words, the hypervisor is ready to serve VM requests in a timely manner, provided that VMs also use the VMBus and VSC design. A VM can still communicate with the hypervisor without VMBus and VSC drivers, but communication for these VMs will be slower, as they will use device emulation rather than kernel access.
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