EN_Virtualization

1. What is virtualization?

Virtualization is a technology that involves creating virtual versions of physical devices or resources within a system. This process allows for the abstraction of physical components into logical units, enhancing flexibility and efficiency in resource usage. Virtualization can be applied to various system aspects, including hardware platforms, storage devices, network resources, and operating systems.

RAID와 LVM

The comparison to RAID and LVM helps to contextualize virtualization within the broader scope of IT infrastructure:

RAID (Redundant Array of Independent Disks): This technology combines multiple physical storage devices, like hard drives, into a single logical unit for improved redundancy and performance. Although commonly associated with Windows systems, RAID is not exclusive to them and can be implemented in various environments.

LVM (Logical Volume Manager): Primarily used in Linux systems, LVM is a method of managing storage that allows for more flexible allocation of space on physical storage devices. It provides a layer of abstraction over physical storage, allowing for resizing and management of storage space without being limited by the physical layout of the disks.

Full-Virtualization vs. Para-Virtualization

Focuses on the level of hardware emulation and interaction between guest OS and the hypervisor:

Full-Virtualization:

• Hardware Emulation: Full-virtualization involves completely emulating the hardware for each virtual machine. The guest OS does not need modifications as it interacts with a simulated hardware environment.
• Guest OS: It can run unmodified operating systems as if they were running on actual hardware.
• Hypervisor Role: The hypervisor manages and abstracts the hardware, offering a virtual hardware layer to each VM.

Para-Virtualization:

• Direct Hypervisor Interface: In para-virtualization, the guest OS is aware that it is running in a virtualized environment and directly communicates with the hypervisor.
• Guest OS: Modifications are required in the guest OS to enable it to interact with the hypervisor API for better performance.
• Performance: It generally offers better performance than full-virtualization, especially in I/O operations, due to lower overhead.

Host Virtualization vs. Container Virtualization vs. Hypervisor Virtualization

Differentiates based on where the virtualization layer sits (on top of an OS, sharing an OS, or directly on hardware) and its operational efficiency and use cases:

Host Virtualization (Type 2 Hypervisor):

• Layering: Runs on top of a host operating system. The hypervisor is a software layer installed on the OS. Use Case: Generally used for development, testing, and educational purposes.
• Example: VMware Workstation, Oracle VirtualBox.

Container Virtualization:

• OS Sharing: Containers share the host OS kernel but isolate the application and its dependencies in a user space.
• Resource Efficiency: More resource-efficient than VMs as they don’t need to emulate a full OS.
• Example: Docker, Kubernetes.

Hypervisor Virtualization (Type 1 Hypervisor):

• Direct Hardware Interface: Runs directly on the system’s hardware to control the hardware and manage guest operating systems.
• Performance: Typically offers better performance and efficiency than host virtualization.
• Example: VMware ESXi, Microsoft Hyper-V.

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