Physical machine is replaced by Host.
Instead installing Operating system in the host. Hypervisors were installed in the host.
Instead running application directly here, Virtual machines are created in the hypervisors and independent OS is installed in each VM. They can be in combination of windows and linux etc.
Hypervisor such as ESXi or Hyper-V are act as intermediary between virtual machine and the hardware. It enable to share common hardware to all VM in the host or server.
Common hardware includes Memory,CPU, Network adapters and Storage adapters.
Hypervisors decide which VM to be allocated with amount of hardware resources.
Types of Hypervisors
- Bare metal - Install hypervisor directly in physical server and referred as baremetal hypervisor. There are many such hypervisor in the market such as VMware, Microsoft, Citrix zen server. The way to install can be done as old fashioned way put CD in the CD drive and install ESXi or Hyper-V. Here Installed Hypervisor have direct access to hardware.
2)Type 2 Hypervisors - have no direct access to the hardware. Here OS is installed in the hardware first and Hypervisor such as VMPlayer, Parallel for mac, is installed on top OS.
Type 1 Hypervisor: VM at top → Hypervisor in middle → Hardware at bottom
Type 2 Hypervisor: VM at top → Hypervisor →OS →Hardware at bottom
Type 2 generally used in personal computer to set up a lab work and Type 1 typically used in data centre.
VM Files and Live State
VM doesn’t have dedicated storage. VM machine will have lot of files to handle and those file are stored in shared storage VM Files and this communication or transfer happen across hypervisor and storage adapters.
Storage adaptors do indeed send traffic to capacity device, which is an integral part of a VM’s live state that enables the virtual machine to operate properly.
This is common storage for all the VM mounted in the host.
VM files are the configuration files for every VM in the host and it act like meta data information about memory and storage for the VM’s. It helps to boot up VM. Virtual disk is needed to boot VM.
VM Consumptions of Resources such as CPU, Memory, Networking, Storage.
CPU Virtualization
CPU has to be allocated for VM’s created. Our duty is when VM’s are created we have to rightsize those VM’s and give them correct CPU count.
Memory Virtualization
When VM launches an application the guest OS in each VM has its own table tracking what call Guest Physical memory or virtual memory but application need actual physical memory so guest physical/virtual memory maps or used actual host physical memory by the hypervisor.
here host physical memory work in two types:
1)VM can reserve required physical memory in host and lock and not share with other VM
2)Host Physical Memory can be shared across all VM as when required based on need.
Virtual Networking
How network resources are delivered to VM?
VM’s created in the host with underlying hypervisor uses vNIC (Virtual Network Interface Card) to connect to Virtual Switch. This Virtual switch enables to communicate or send/receive data to other VM’s in same Virtual LAN in the host.
The data comes out of VM’s are absorbed by hypervisor and hypervisor pointing to appropriate Virtual Switch.
Virtual Switch uses pNIC (physical NIC) to connect physical switch and this physical switch can help to connect outside internet, router, other VLAN or other data centers.
Storage
OS in any machine needs storage.
OS in the VM may not know they dont have actual storage. To mimic VM have storage we use vSCSI controller. When OS have to carryout some sort of storage command, it relies on vSCSI controller.
OS stores file through sending SCSI command sent to vSCSI. VSCSI pass it to hypervisor.Hypervisor determines the appropriate location for the virtual disk to sent it out through storage adapter. Storage command arrive at data store. Changes actually written in the file that contains the virtual machines virtual disk.
Storage adapter helps to send SCSI command from hypervisor to the storage array.
Data Store can relocate files to different Storage array present in different network.
Hypervisor also supports pass files to another storage array present in different Ethernet network.
VM’s running in specific host can move to different network as long as Data store supports connected to the new host and provide all supporting files needed.
Virtualization Benefits
Maximize investment on the hardware and not wasting money that we never going to utilize.
Hypervisor enable to have multiple VM with required OS in each and allocate resource paid effectively and not overburdening them.
Mobility
Moving VM to different host for better performance, resource utilization and no downtime.
