How Vmware ESX hardware virtualization Works

By using software, a virtual machine behaves like a physical machine and has its own set of virtual hardware, including the operating system and applications it uploads into. With virtualization, each virtual machine has a consistent set of virtual hardware, regardless of the operating system running on the host server below. This series of articles is designed to help VMware system administrators better understand the internal work of virtual machines and help manage the infrastructure on a daily basis.

When you create a virtual machine, you have assigned a set of default settings to the virtual machines. You can also add or remove the additional virtual hardware that you want by editing the following configurations.

In addition to hard disks, most virtual hardware can only be added or removed after the virtual organization is closed. The following table outlines the list of virtual hardware that can be added to a VMware ESX 3.5 host virtual machine. This table includes the maximum number of devices owned by a virtual machine, as well as hardware that can be added, removed, or modified when the VM is running or shutting down.

When you add a hard disk to the virtual machine, you will use the existing SCSI controller (this is the first hardware driver in the VM and the SCSI controller will be added automatically). This is a default setting. You can add up to 60 hard drives or 15 SCSI controllers to the virtual machine. You can set the virtual driver node ID (i.e. 0:0) by combining the number of drive drives with the number of controllers. When you add a new hard disk, the number of devices may increase until all device slots are exhausted (up to 15). Then add additional SCSI controllers (1 to 3) according to the needs of the additional disks. You can also choose to manually set the virtual device Node ID to force it to add another controller.

If you select a virtual device node ID that is not present on the controller, the new controller will be added. You can only see the ID that all SCSI controllers can use, which can be added based on a free PCI slot. If there is only one network interface card in the virtual machine, you can add up to four, and if you have two network interface cards, add up to three. When you turn off a virtual machine, the virtual device Node ID is also tender to change on the existing drive, just be careful, this may change the operating system driver, and may fail when you start the virtual machines.

Note about memory: You can assign more memory to a virtual machine than a physical host, up to a maximum of 64GB. For example, a host with 16GB of memory can run a virtual machine with 32GB memory. This is because a. VSWP disk file was created when the virtual machine was started, the same size as the memory allocated to the virtual machine. Of course, even if you allocate more memory to the host, this process will result in performance loss, and be careful not to run out of all the physical memory.

Now that we know that virtual machines have virtual hardware, what kind of hardware is presented through the host? The following figure is the virtual hardware that is seen on the ESX 3.5 host. Note that depending on the physical host system and the virtual machine operating system, some hardware may be slightly different. You can get the information shown in the diagram by looking at Windows Device Manager and using the System Information tool.