Types of Server Virtualization
Virtualization of a server is the distribution of a physical server into the number of small virtual servers, each running its own operating system. These operating systems are known as Hosting Operating Systems. These are run on another operating system known as the host operating system. Any guest who runs like this does not know any other guest who runs on the same host. To achieve this transparency we use various virtualization techniques.
Types of server virtualization:
1. Hypervisor -
Hypervisor or VMM (virtual device controller) is a layer that comes between the operating system and hardware. It provides the necessary services and functions for the smooth operation of multiple operating systems.
Identifies traps, answers to privileged CPU and queue handles, send, and restore hardware requirements. The host operating system is also running at the top of the hypervisor to manage and manage virtaul devices.
2. Para Virtualization -
It’s based on a hypervisor. This model addresses most of the emulation and excitement over the head in program-implemented virtualization. The catering operating system is modified and translated before installing it in a virtual machine.
Due to the change in the host operating system, the performance improves, because the modified operating system of the operating system communicates directly with the hypervisor and eliminates the emulation.
Example: Xen primarily uses Para Virtualization, where a customized Linux environment is used that supports an administrative environment known as domain 0
No emulation overhead
Requires a roaming operating system change
3. Complete virtualization -
It is very similar to Virtualization of Para. Where necessary, it can simulate basic hardware. The hypervisor stops the operations of the device that the operating system uses to perform I / O or change the state of the system. After capture, these operations are emulated in the software and the status codes return very much in line with what real hardware would bring. Therefore, an unmodified operating system is able to run at the top of the hypervisor.
For example, the VMWare ESX server uses this method. As an administrative operating system, a customized version of Linux, known as the Service Console, is used. This is not as fast as Para virtualization.
No need to modify the host operating system.
Slower due to emulation
Problems when installing a new device driver.
4. Hardware-supported virtualization
Similarly, the Full Virtualization and Para virtualization function, unless it requires hardware support. A large part of the hypervisor, which is the result of capturing and emulating V / I operations and state instructions performed in the host operating system, relies on the x86 hardware extensions.A non-standard OS can be started because it would use hardware virtualization support to process hardware access requests, privileged and secure operations, and to communicate with a virtual computer.
Examples: AMD — V Pacifica and Intel VT Vanderpool offer hardware support for virtualization.
No need to modify the host operating system.
Very few hypervisors
Required hardware support
5. Virtualization at the core level -
Instead of using a hypervisor, it starts a separate version of the Linux kernel and sees the connected virtual machine as a user space process on the physical host. This facilitates the launch of several virtual devices on a single host. The device driver is used to communicate between the main Linux kernel and the virtual computer.
Virtualization requires processor support (Intel VT or AMD-v). A slightly modified QEMU process is used as display and execution containers for virtual machines. In many ways, virtualization at the kernel level is a specialized form of virtualization for servers.
Examples: Linux (UML) and Virtual Kernel Machine (KVM)
No special administrative software required.
Very few overheads
The required hardware support
6. System Level or OS Virtualization -
It runs more but logically different environments on a single kernel of the operating system. A common kernel approach is also called, since all virtual machines have a common core of the host operating system. Based on the concept of root substitution “chroot”.
chroot starts during startup. The kernel uses root file systems to load drivers and performs other tasks of the initial phase of the system. It then switches to another root file system using the chroot command to install the file system on a disk as its final root file system and then proceeds to system initialization and configuration in that file system.A virtual virtualization virtualization mechanism is the extension of this concept.
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