Join Brandon Neill for an in-depth discussion in this video Why virtual machines?, part of VMware vSphere 6 Essential Training.
- Before we begin building a lab environment, let's take a look at what a virtual machine is and why we would want to use one. A virtual machine is a software defined computer that runs inside of another computer. A physical computer is defined by the hardware we place inside of it. How many CPU's, how much memory, and any other devices that are installed on that physical computer. A virtual machine, in contrast, is encapsulated in a set of files. One of these files determines the hardware for that virtual machine.
VM's can have largely the same hardware as physical computers, including, network interface cards, hard drives, USB devices, and SCSI devices. Virtual machines use the same operating system and applications as a physical computer. From the point of view of the operating system, it can't tell whether it is running in a virtual machine. So why would we want to use a virtual machine? A common reason for using a VM, is server consolidation. A physical computer is typically using about 15 to 25 percent of its CPU.
And the other resources, such as memory, network, and storage, aren't being fully utilized either. By running multiple VM's inside of the same host, we can increase the CPU utilization up to 60 to 80 percent, and get better utilization of the other resources as well. Another reason for using a virtual machine is hardware independence. Because a virtual machine abstracts the underlying physical hardware, the same virtual machine can be run on multiple hardware types, without having to make any changes inside the virtual machine.
Because virtual machines are encapsulated as a set of files, they provide for better mobility and duplication. Anything that you can do with a set of files, you can do with a VM. Including, transferring it across the country, making backups, and making multiple copies of it. Virtual machines reduce downtime, because we can move a live-running virtual machine from one host to another host. This means that hardware maintenance no longer requires downtime. The platform that a virtual machine runs on top of, is called the hypervisor.
The hypervisor is responsible for scheduling CPU. All of the virtual machines running on a host, run directly on a CPU. But the hypervisor manages scheduling to ensure that each virtual machine gets the CPU that it's entitled to. The hypervisor is also responsible for sharing the physical memory among all of the running virtual machines. Other types of hardware are emulated by the hypervisor. Including, SCSI controllers, network interface cards, and USB controllers. There are two types of hypervisors that are available.
A bare-metal hypervisor, and a hosted hypervisor. A bare-metal hypervisor has less overhead, and better performance, because it is running on top of the physical hardware. Examples of a bare-metal hypervisor include ESXi, and Citrix Zenserver. A hosted hypervisor, while it has less performance because it is running on top of an operating system, does provide for more flexibility and easier management.
Examples of a hosted hypervisor include VMware Workstation, and VMware Fusion. Most production environments run on top of a bare-metal hypervisor, such as, ESXi, while many lab environments run on top of a hosted hypervisor, such as, VMware Workstation. In this course, I will be using VMware Workstation to create an ESXi environment.
This course teaches the basics of installing, configuring, and maintaining vSphere 6, including installation of the ESXi hypervisor and vCenter Server using a pre-created environment called AutoLab. Following lab creation, Brandon Neill introduces the core components of vSphere (ESXi and vCenter) and shows how to configure storage and networking. Finally, he runs through some typical virtual-machine management tasks, such as creating a virtual machine manually vs. creating one with templates and clones, working with snapshots, and performing a vMotion migration.
- Recognize the purpose of the vCenter server in a lab environment.
- Identify the correct settings needed to create a virtual network.
- Explain how to correct a duplicate IP address issue.
- Understand the difference between iSCSI interfaces and virtual machine interfaces.
- Describe the steps in the process of cloning.
- Recall how to revert back to previous stages of a snapshot chain.