Virtualization at a low level involves creating a virtual version of a computing resource, such as a server, storage device, or network, using specialized software called a hypervisor. Here’s a detailed explanation of how it works:
Hypervisor
The hypervisor is the core component that enables virtualization. It acts as an intermediary between the physical hardware and the virtual machines (VMs). There are two types of hypervisors:
Type 1 (Bare-Metal) Hypervisors: These run directly on the physical hardware. Examples include VMware ESXi, Microsoft Hyper-V, and Citrix XenServer. They are highly efficient because they interact directly with the hardware without needing a host operating system[9][18].
Type 2 (Hosted) Hypervisors: These run on top of a host operating system. Examples include VMware Workstation and Oracle VirtualBox. They are easier to install and use but might be less efficient than Type 1 hypervisors[9][18].
Virtual Machine Creation
When a hypervisor is installed on a physical machine, it can create multiple VMs. Each VM operates as a separate computer with its own operating system (guest OS) and applications. Here’s how it works:
Resource Allocation: The hypervisor allocates physical resources such as CPU, memory, and storage to each VM. These resources are abstracted and presented to the VMs as virtual hardware[9][18].
Isolation: Each VM is isolated from the others, meaning that the operations of one VM do not affect the others. This isolation is crucial for security and stability[9][18].
Guest OS: Each VM runs its own guest OS, which can be different from the host OS. The guest OS performs all necessary startup activities, such as bootstrapping and loading the kernel, just like it would on a physical machine[9][18].
Virtualization Process
The virtualization process involves several steps:
Instruction Set Emulation: The hypervisor intercepts and emulates the instructions from the guest OS to the physical CPU. This allows the guest OS to run as if it were on its own dedicated hardware[15].
Memory Management: The hypervisor manages the memory allocation for each VM. It uses techniques like memory ballooning and page sharing to optimize memory usage[9][18].
I/O Virtualization: The hypervisor virtualizes input/output operations, allowing VMs to share physical I/O devices like network cards and storage devices. This is done through virtual network adapters and virtual disk files[9][18].
