What is a Hypervisor?
If you know what a private cloud is and you know the infrastructure of it, you’ve probably heard about hypervisor.
It is the part of the private cloud that manages the virtual machines, i.e. it is the part (program) that enables multiple operating systems to share the same hardware. Each operating system could use all the hardware (processor, memory) if no other operating system is on. That is the maximum hardware available to one operating system in the cloud.
Virtualization is changing the mindset from physical to logical.
What virtualization means is creating more logical IT resources, called virtual systems, within one physical system. That’s called system virtualization. It most commonly uses the hypervisor for managing the resources for every virtual system. The hypervisor is a software that can virtualize the hardware resources.
Nevertheless, the hypervisor is what controls and allocates what portion of hardware resources each operating system should get, in order every one o them to get what they need and not to disrupt each other.
Hypervisors are virtual machine monitor(VMM) that enables numerous virtual operating systems to simultaneously run on a computer system. These virtual machines are also referred as guest machines and they all share the hardware of the physical machine like memory, processor, storage and other related resources. This improves and enhances the utilization of the underlying resources.
The hypervisor isolates the operating systems from the primary host machine. The job of a hypervisor is to cater to the needs of a guest operating system and to manage it efficiently. Each virtual machine is independent and do not interfere with each another although they run on the same host machine. They are no way connected to one another. Even at times one of the virtual machines crashes or faces any issues, the other machines continue to perform normally.
There are two types of hypervisors:
Type 1 hypervisor: hypervisors run directly on the system hardware – A “bare metal” embedded hypervisor,
Type 2 hypervisor: hypervisors run on a host operating system that provides virtualization services, such as I/O device support and memory management.
Type 1 hypervisors:
1. VMware ESX and ESXi
These hypervisors offer advanced features and scalability, but require licensing, so the costs are higher.
There are some lower-cost bundles that VMware offers and they can make hypervisor technology more affordable for small infrastructures.
VMware is the leader in the Type-1 hypervisors. Their vSphere/ESXi product is available in a free edition and 5 commercial editions.
2. Microsoft Hyper-V
The Microsoft hypervisor, Hyper-V doesn’t offer many of the advanced features that VMware’s products provide. However, with XenServer and vSphere, Hyper-V is one of the top 3 Type-1 hypervisors.
It was first released with Windows Server, but now Hyper-V has been greatly enhanced with Windows Server 2012 Hyper-V. Hyper-V is available in both a free edition (with no GUI and no virtualization rights) and 4 commercial editions – Foundations (OEM only), Essentials, Standard, and Datacenter. Hyper-V
3. Citrix XenServer
It began as an open source project. The core hypervisor technology is free, but like VMware’s free ESXi, it has almost no advanced features. Xen is a type-1 bare-metal hypervisor. Just as Red Hat Enterprise Virtualization uses KVM, Citrix uses Xen in the commercial XenServer.
Today, the Xen open source projects and community are at Xen.org. Today, XenServer is a commercial type-1 hypervisor solution from Citrix, offered in 4 editions. Confusingly, Citrix has also branded their other proprietary solutions like XenApp and XenDesktop with the Xen name.
4. Oracle VM
The Oracle hypervisor is based on the open source Xen. However, if you need hypervisor support and product updates, it will cost you. Oracle VM lacks many of the advanced features found in other bare-metal virtualization hypervisors.
Type 2 hypervisor
1. VMware Workstation/Fusion/Player
VMware Player is a free virtualization hypervisor.
It is intended to run only one virtual machine (VM) and does not allow creating VMs. VMware Workstation is a more robust hypervisor with some advanced features, such as record-and-replay and VM snapshot support.
VMware Workstation has three major use cases:
for running multiple different operating systems or versions of one OS on one desktop,
for developers that need sandbox environments and snapshots, or
for labs and demonstration purposes.
2. VMware Server
VMware Server is a free, hosted virtualization hypervisor that’s very similar to the VMware Workstation. VMware has halted development on Server since 2009
3. Microsoft Virtual PC
This is the latest Microsoft’s version of this hypervisor technology, Windows Virtual PC and runs only on Windows 7 and supports only Windows operating systems running on it.
4. Oracle VM VirtualBox
VirtualBox hypervisor technology provides reasonable performance and features if you want to virtualize on a budget. Despite being a free, hosted product with a very small footprint, VirtualBox shares many features with VMware vSphere and Microsoft Hyper-V.
5. Red Hat Enterprise Virtualization
Red Hat’s Kernel-based Virtual Machine (KVM) has qualities of both a hosted and a bare-metal virtualization hypervisor. It can turn the Linux kernel itself into a hypervisor so the VMs have direct access to the physical hardware.