Layer 1 & Layer 2 Hypervisor - A common misconception of Hyper-V

In the world of Server Virtualization, there are two types of hypervisors:

*️⃣𝐋𝐚𝐲𝐞𝐫 2 hypervisors are installed as an application (or service) on an existing operating system (such as Microsoft Windows). E.g.: VMware Virtual Box, Oracle Virtual box.

*️⃣𝐋𝐚𝐲𝐞𝐫 1 hypervisors are in and of themselves operating systems that are installed on the ‘bare metal’ – directly on the hardware. E.g.: VMware Esxi, Citrx Xen server, KVM.

*️⃣𝑻𝒉𝒆 𝒉𝒚𝒑𝒆𝒓𝒗𝒊𝒔𝒐𝒓 is the virtualization layer – the platform on which the virtual servers are hosted. Because all operating systems require resources, it is axiomatic that the Layer 1 Hypervisors – those that are themselves thin operating systems – are going to be more efficient than the Layer 2 Hypervisors, which have to first allow the parent operating system to take the resources that it requires, and then meter out the available resources to its applications and services as it sees fit.

👉So, in which category does a Microsoft Hyper-V comes in?

🔵When you install Hyper-V, you think it's being installed on top of a host OS, but it is not. The setup converts the original OS in something like a VM and puts the hypervisor below. This is what is called the root or parent partition of Hyper-V.

🔵 Hyper-V is installed beneath the operating system. The host OS itself becomes a virtual machine. This change is transparent to users and applications because the host can continue to access the hardware directly.

Hyper-V consists of a hypervisor layer upon which there is a Parent partition and possibly any number of Child partitions. The parent partition contains the host operating system. Child partitions are created by the host and contain guest operating systems which run alongside the parent partition.

🔵Hyper-V uses hardware-assisted virtualization technology to grant the parent partition direct hardware access, while giving child partitions only a virtualized set of hardware.

✅ Because most existing device drivers and applications on the host OS (which resides in the parent partition) can access the hardware as if no hypervisor is present, enabling the Hyper-V role is generally transparent to users and applications. The system provides the appearance that the hypervisor and any guests run on the top of the host operating system, even though the hypervisor sits beneath the host with guests running side-by-side.

 Thus, this clearly explains Hyper-V which looks like a Type-2 hypervisor is actually a Type-1 hypervisor!