Hypervisors
My notes on Hypervisors paraphrased from TechTarget articles -
Hypervisors enable efficient use of resources, isolation, and easier management of virtualised environments in the underlying hardware.
A hypervisor makes the underlying hardware details irrelevant to the VMs.
A VM is essentially little more than code operating in a server's memory space. Snapshot tools can quickly capture the content of that VM's memory space and save it to disk in moments.
A hypervisor, also known as a virtual machine monitor (VMM), creates and manages guest virtual machines (VMs) on a physical host system by allowing multiple operating systems to run simultaneously on a single physical machine.
A hypervisor makes the underlying hardware details irrelevant to the VMs.
A VM is essentially little more than code operating in a server's memory space. Snapshot tools can quickly capture the content of that VM's memory space and save it to disk in moments.
There are two types of hypervisors: Type 1, or "bare-metal" runs directly on the hardware, while Type 2 runs on a host operating system.
"Bare metal" hypervisors are the most common and popular type of hypervisor for the enterprise data center. They are deployed directly atop the system's hardware without any underlying operating systems or other software and are often more efficient and have a smaller overhead than Type 2 hypervisors.
Examples of bare-metal virtualization hypervisors
* VMware ESX and ESXi - most mature hypervisor technology by far, but can be expensive to implement because of its higher licensing costs.
* Microsoft Hyper-V has tight Windows integration & may be the best hypervisor for organizations that don’t require a lot of bells and whistles.
* Citrix XenServer is a mature platform that began as an open source project.
* Oracle VM is Oracle’s homegrown hypervisor technology based on open source Xen. It’s certified with most of Oracle’s other products and therefore includes no-hassle support.
"Hosted" hypervisors like VMware Player or Parallels Desktop run as a software layer atop a host operating system. Hosted hypervisors are often found on endpoints like PCs. They are often easier to install and use than Type 1 hypervisors.
Hosted virtualization hypervisors - can only run a single virtual machine (VM) and does not allow you to create VMs.
* VMware Player is a free virtualization hypervisor
* VMware Workstation is a more robust hypervisor useful for running multiple different operating systems or versions of one OS on one desktop
* VMware Fusion is the Mac version of Workstation
* VMware Server - no-frills hosted hypervisor and alternative to using the free version of ESXi.
* Microsoft Virtual PC - free, only supports running Windows operating systems on it
* Oracle VM VirtualBox - Despite being a free, hosted product with a very small footprint, VirtualBox shares many features with VMware vSphere and Microsoft Hyper-V. Decent alternative to more expensive hypervisors for both server and desktop virtualization.
* Red Hat’s Kernel-based Virtual Machine (KVM) has qualities of both a hosted and a bare-metal virtualization hypervisor.
* Parallels Desktop for Mac hypervisor is very similar to VMware Fusion.
Storage hypervisors, a key element of software-defined storage, are used to virtualize all of the storage resources in the environment to create centralized storage pools that administrators can provision -- without having to concern themselves with where the storage was physically located.
"Bare metal" hypervisors are the most common and popular type of hypervisor for the enterprise data center. They are deployed directly atop the system's hardware without any underlying operating systems or other software and are often more efficient and have a smaller overhead than Type 2 hypervisors.
Examples of bare-metal virtualization hypervisors
* VMware ESX and ESXi - most mature hypervisor technology by far, but can be expensive to implement because of its higher licensing costs.
* Microsoft Hyper-V has tight Windows integration & may be the best hypervisor for organizations that don’t require a lot of bells and whistles.
* Citrix XenServer is a mature platform that began as an open source project.
* Oracle VM is Oracle’s homegrown hypervisor technology based on open source Xen. It’s certified with most of Oracle’s other products and therefore includes no-hassle support.
"Hosted" hypervisors like VMware Player or Parallels Desktop run as a software layer atop a host operating system. Hosted hypervisors are often found on endpoints like PCs. They are often easier to install and use than Type 1 hypervisors.
Hosted virtualization hypervisors - can only run a single virtual machine (VM) and does not allow you to create VMs.
* VMware Player is a free virtualization hypervisor
* VMware Workstation is a more robust hypervisor useful for running multiple different operating systems or versions of one OS on one desktop
* VMware Fusion is the Mac version of Workstation
* VMware Server - no-frills hosted hypervisor and alternative to using the free version of ESXi.
* Microsoft Virtual PC - free, only supports running Windows operating systems on it
* Oracle VM VirtualBox - Despite being a free, hosted product with a very small footprint, VirtualBox shares many features with VMware vSphere and Microsoft Hyper-V. Decent alternative to more expensive hypervisors for both server and desktop virtualization.
* Red Hat’s Kernel-based Virtual Machine (KVM) has qualities of both a hosted and a bare-metal virtualization hypervisor.
* Parallels Desktop for Mac hypervisor is very similar to VMware Fusion.
Storage hypervisors, a key element of software-defined storage, are used to virtualize all of the storage resources in the environment to create centralized storage pools that administrators can provision -- without having to concern themselves with where the storage was physically located.
As with storage, network virtualization can enable a software-defined network or software-defined data center platforms.
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