1)What is a virtual machine?
A Virtual Machine (VM) is a compute resource that uses software instead of a physical
computer to run programs and deploy apps. One or more virtual “guest” machines run
on a physical “host” machine. Each virtual machine runs its own operating system and
functions separately from the other VMs, even when they are all running on the same
host. This means that, for example, a virtual MacOS virtual machine can run on a
physical PC.
Virtual machine technology is used for many use cases across on-premises and cloud
environments. More recently, public cloud services are using virtual machines to
provide virtual application resources to multiple users at once, for even more cost
efficient and flexible compute.
2) Objectives of a virtualization system
One of the main uses of virtual machines is in systems development. These tools can
be applied for specific tests, in a beta release of the product, for example. In cases
where the application's operating system is different from that used for development,
programmers are able to carry out the tests without having to install a new OS on the
main computers.
3) Advantages and disadvantages of a virtualization system
Advantages of virtual machines
Because the software is separate from the physical host computer, users can run
multiple OS instances on a single piece of hardware, saving a company time,
management costs and the physical space. Another advantage is that VMs can support
legacy apps, reducing or eliminating the need and cost of migrating an older app to an
updated or different operating system.
In addition, developers use VMs in order to test apps in a safe, sandboxed
environment. This can also help isolate malware that might infect a given VM instance.
Since software inside a VM cannot tamper with the host computer, malicious software
cannot spread as much damage.
Virtual machine downsides
Virtual machines do have a few disadvantages. Running multiple VMs on one physical
host can result in unstable performance, especially if infrastructure requirements for a
particular application are not met. This also makes them less efficient in many cases
when compared to a physical computer. Most IT operations utilize a balance between
physical and virtual systems.
4) Options of system of virtualization
1º. Vmware VSphere / VCenter Server
vSphere is an industry-level virtualization platform and a foundation for a cloud-based
infrastructure. The vCenter Server is a centralized platform for managing vSphere
environments. It allows you to assign custom roles to users, create new VMs, search
the vCenter Server inventory, etc.
2º. Microsoft Hyper-V
To start off, here's a basic Hyper-V definition: Hyper-V is a Microsoft technology that
allows users to create virtual computer environments, and run and manage multiple
operating systems on a single physical server.
3º. Linux KVM
KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86
hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a
loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and
a processor specific module, kvm-intel.ko or kvm-amd.ko.
Using KVM, one can run multiple virtual machines running unmodified Linux or
Windows images. Each virtual machine has private virtualized hardware: a network
card, disk, graphics adapter, etc.
4º. XenServer
XenServer is among the virtualization solutions provided by Citrix Systems, which
consolidates a physical server's computing power into multiple virtual machines, all
emulating as a standard server. Citrix XenServer is built to provide the operational
requirements of a standard server and supports most server operating systems, such
as Linux and Windows Server, on guest server machines.
Through its virtual machine monitoring component, Citrix XenServer manages the
allocation and distribution of physical server computing resources among virtual
machines and administers their performance and use.
Bibliografia
https://www.networkworld.com/article/3583508/what-is-a-virtual-machine-and-why-are-
they-so-useful.html
https://www.makeuseof.com/tag/reasons-start-using-virtual-machine/
https://www.arles-santana.com.br/2017/07/11/qual-a-melhor-plataforma-de-
virtualizacao-ou-hypervisor/
https://www.linux-kvm.org/page/Main_Page
https://www.techopedia.com/definition/28436/citrix-xenserver
