Resource sharing explained, CPU Virtualization

Resource sharing explained

In virtualization, physical resources are shared among virtual machines. Resource sharing represents perhaps the most significant advantage of server virtualization, because you can allocate resources to a VM based on the machine’s actual performance needs. Multiple virtual machines can run on the same physical host, with each virtual machine sharing the resources of the host. Virtual machines share access to CPUs, physical network cards, disk controllers, and are assigned their own region of memory.
On the same physical host, different virtual machines can run different operation systems. For example, you can run virtual machines that run some Linux distributions and virtual machines that run Windows on the same host.
When multiple virtual machines run on the same host, each virtual machine is allocated a portion of its physical resources. The hypervisor allows multiple operating systems to share a single hardware host.

With the default settings, all VMs on the same ESXi host receive an equal share of resources available.


What is CPU virtualization?

CPU virtualization involves a single CPU acting as if it were multiple separate CPUs. The most common reason for doing this is to run multiple different operating systems on one machine. CPU virtualization emphasizes performance and runs directly on the available CPUs whenever possible. The underlying physical resources are used whenever possible and the virtualization layer runs instructions only as needed to make virtual machines operate as if they were running directly on a physical machine.
When many virtual machines are running on an ESXi host, those virtual machines might compete for CPU resources. When CPU contention occurs, the ESXi host time-slices the physical processors across all virtual machines so each virtual machine runs as if it has its specified number of virtual processors.

Note that the CPU virtualization is not the same thing as emulation. With emulation, all operations are run in software by an emulator. The emulator emulates the original computer’s behavior by accepting the same data or inputs and achieving the same results.


Physical and virtualized host memory

In a nonvirtual environment, the operating system assumes it owns all physical memory available. When an application starts, it uses interfaces provided by the OS to allocate or release virtual memory pages during the execution. Virtual memory is a technique used in most operating systems, and is supported by almost all modern CPUs. Virtual memory creates a uniform virtual address space for applications and allows the OS and hardware to handle the address translation between the virtual and physical address space. This technique adapts the execution environment to support large address spaces, process protection, file mapping, and swapping in modern computer systems.
In a vSphere environment, the VMware virtualization layer creates a contiguous addressable memory space for the virtual machine when it is started. The allocated memory space is configured when the virtual machine is created and has the same properties as the virtual address space. This configuration allows the hypervisor to run multiple virtual machines simultaneously while protecting the memory of each virtual machine from being accessed by others.


Virtualization : vSphere overview


VMware vSphere components

VMware vSphere is a software suite that includes components like ESXi, vCenter Server, vSphere Client, vCenter Orchestrator, vSphere Update Manager, etc. vSphere components provide virtualization, management, resource optimization and many other features useful for a virtual environment.

vSphere is used to virtualize and aggregate the underlying physical hardware resources and to provide the pool of virtual resources to the data center. It also supports some advanced virtualization features such as

  • disaster recovery
  • high availability
  • fault tolerance
  • dynamic resource allocation, etc.
  • People new to the VMware’s virtualization platform sometimes get confused in dealing with vSphere and its components. Remember that vSphere is a suite of products, just like Microsoft Office (a suite of office products such as Word, Excel, Access), and not a single product that you can install in your environment.
    Here is a list and description of the most important components included in the vSphere product suite:
  • ESXi – a type 1 hypervisor. A hypervisor is a piece of software that creates and runs virtual machines. In vSphere, virtual machines are installed on ESXi servers.
  • vCenter Server – a centralized management platform and framework that lets you manage virtual machines and ESXi hosts centrally.
  • vSphere Update Manager – an add-on package for vCenter Server that helps you keep your ESXi hosts and VMs patched with the latest updates.
  • vSphere Web Client – a web-based user interface used for managing a virtual infrastructure.
  • vSphere Client – a locally installed Windows application with a graphical user interface (GUI) for all day-to-day management tasks and for the advanced configuration of a virtual infrastructure.
  • There are three vSphere editions:
    vSphere Standard
    vSphere Enterprise
    vSphere Enterprise Plus
  • :

    Why use virtualization?

There are many reasons why you should consider to use virtualization in your environment. Here are some of them:
server consolidation – virtualization can help you conserve physical space. In traditional data center environments it is common to dedicate each server to a single application. This leaves most computers vastly underused. Virtualization enables you to run more workloads on a single server, which reduces the number of physical machines in your environment.
reduced cost – hardware is most often the highest cost in a data center. Because virtualization reduces the need for physical machines, the cost also goes down. But the cost goes well beyond that of hardware – software licensing savings, power and cooling cost reduction, improved user accessibility and performance are also some of the ways to reduce your cost.
increased uptime – VMware offers a number of advanced features that are not available on physical servers, which helps with business continuity and increased uptime. Such capabilities are live migration, storage migration, fault tolerance, high availability, etc. These technologies keep virtual machines running or give them the ability to quickly recover from unplanned outages. The ability to quickly and easily move a virtual machine from one server to another is perhaps one of the greatest single benefits of virtualization with far-reaching uses.
faster server provisioning – with VMware, you can quickly clone an image, master template, or existing virtual machine to get a server up and running within minutes. This is in contrast to physical servers, which usually require hours for installation.
easier backups – with virtualization, you can create full backups of your virtual machines within minutes. These backups can be moved from one server to another and redeployed easier and faster. You can also take a snapshot of a virtual machine, which is a state of a virtual machine at a specific point in time


What is Vmware ?

From VMware Virtualization for Desktop & Server, Application, Public & Hybrid Clouds

About VMware

VMware is the leader in virtualization and cloud infrastructure solutions that enable businesses to thrive in the Cloud Era. Customers rely on VMware to help them transform the way they build, deliver and consume Information Technology resources in a manner that is evolutionary and based on their specific needs. With 2015 revenues of $6.6 billion, VMware has more than 500,000 customers and 75,000 partners. The company is headquartered in Silicon Valley with offices throughout the world and can be found online at VMware Virtualization for Desktop & Server, Application, Public & Hybrid Clouds.

My words:

VMware is a software company, initially successful and well known for its server virtualisation range of products, branded vSphere.

VMware now offers a range of software products and suites primarily aimed at virtualisation of the data center in the compute, network and storage areas, with management and automation layered around the other offerings.

In addition, VMware offers software in the Desktop Mobility category, enabling the virtualisation of desktops, the management of mobile devices and much more.