Server Virtualization is the partitioning of a physical server into a number of small virtual servers, each running its own operating system. These operating systems are known as guest operating systems. These are running on another operating system known as the host operating system. Each guest running in this manner is unaware of any other guests running on the same host. Different virtualization techniques are employed to achieve this transparency. Show Types of Server virtualization : 1. Hypervisor – A Hypervisor or VMM(virtual machine monitor) is a layer that exists between the operating system and hardware. It provides the necessary services and features for the smooth running of multiple operating systems. It identifies traps, responds to privileged CPU instructions, and handles queuing, dispatching, and returning the hardware requests. A host operating system also runs on top of the hypervisor to administer and manage the virtual machines. 2. Para Virtualization – It is based on Hypervisor. Much of the emulation and trapping overhead in software implemented virtualization is handled in this model. The guest operating system is modified and recompiled before installation into the virtual machine. Example: Xen primarily uses Paravirtualization, where a customized Linux environment is used to support the administrative environment known as domain 0. Advantages:
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3. Full Virtualization – It is very much similar to Paravirtualization. It can emulate the underlying hardware when necessary. The hypervisor traps the machine operations used by the operating system to perform I/O or modify the system status. After trapping, these operations are emulated in software and the status codes are returned very much consistent with what the real hardware would deliver. This is why an unmodified operating system is able to run on top of the hypervisor. Example: VMWare ESX server uses this method. A customized Linux version known as Service Console is used as the administrative operating system. It is not as fast as Paravirtualization. Advantages:
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4. Hardware-Assisted Virtualization – It is similar to Full Virtualization and Paravirtualization in terms of operation except that it requires hardware support. Much of the hypervisor overhead due to trapping and emulating I/O operations and status instructions executed within a guest OS is dealt with by relying on the hardware extensions of the x86 architecture. Unmodified OS can be run as the hardware support for virtualization would be used to handle hardware access requests, privileged and protected operations, and to communicate with the virtual machine. Examples: AMD – V Pacifica and Intel VT Vanderpool provide hardware support for virtualization. Advantages:
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5. Kernel level Virtualization – Instead of using a hypervisor, it runs a separate version of
the Linux kernel and sees the associated virtual machine as a user-space process on the physical host. This makes it easy to run multiple virtual machines on a single host. A device driver is used for communication between the main Linux kernel and the virtual machine. Examples: User – Mode Linux( UML ) and Kernel Virtual Machine( KVM ) Advantages:
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6. System Level or OS Virtualization – Runs multiple but logically distinct environments on a single instance of the operating system kernel. Also called shared kernel approach as all virtual machines share a common kernel of host operating system. Based on the change root concept “chroot”. Examples: FreeVPS, Linux Vserver, and OpenVZ are some examples. Advantages:
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Reference: Which of these is not a benefit of server virtualization?Server virtualization causes, not reduces, network bandwidth hot spots. Therefore, reducing network bandwidth hot spots is not a benefit of server virtualization. Server virtualization is the process of using a virtual machine (VM) hypervisor to create and maintain multiple server VMs on a single hardware server.
What are the three different methods used for server virtualization?There are three ways to create virtual servers: full virtualization, para-virtualization and OS-level virtualization.
What are the implementation levels of virtualization?Implementation Levels of Virtualization In Cloud Computing. 1) Instruction Set Architecture Level (ISA) ISA virtualization can work through ISA emulation. ... . 2) Hardware Abstraction Level (HAL) ... . 3) Operating System Level. ... . 4) Library Level. ... . 5) Application Level.. What are 3 benefits of server virtualization?The benefits of server virtualization are:
Improved server reliability and availability, Lower total operational cost. More efficient utilization of physical servers. More efficient utilization of power.
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