Before we list the top 5 enterprise type 1 hyerpvisors, you might be wondering, "what is a type 1 hypervisor"? If you don't already know, read our post What Is a Type 1 Hypervisor? A hypervisor is software that runs virtual machines inside but there are multiple types so, bottom line, make sure you read the "type 1 hypervisor" article.
Here is the top 5 hypervisor list, in reverse order, just like David Letterman does it...
The open-source KVM (or Kernel-Based Virtual Machine) is a Linux-based type-1 hypervisor that can be added to a most Linux operating systems including Ubuntu, SUSE, and Red Hat Enterprise Linux. It supports most common Linux operating systems, Solaris, and Windows. Most hypervisors that offer KVM offer additional management tools on top such as Red Hat's Virtual Machine Manager.
Red Hat Enterprise Virtualization (RHEV) is a commercial implementation of the KVM Type-1 hypervisor. Red Hat Enterprise Virtualization uses SPICE protocol and VDSM (Virtual Desktop Server Manager) with a RHEL-based centralized management server. RHEV offers support the following 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. In 2007 Citrix bought XenSource, Inc, who supported Xen. Today, the Xen open source projects and community are at Xen.org. Today, XenServer is a commercial tier-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. XenServer offers features such as:
You can find out more about the XenServer editions and features here.
Along with XenServer and vSphere (next on the list), Hyper-V is one of the top 3 Tier-1 hypervisors (frequently flip/flopping between 2nd and 3rd place with XenServer). First released with Windows Server, Hyper-V has now 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 offers:
The leader in the Tier-1 hypervisors is VMware with their vSphere/ESXi product - available in a free edition and 5 commercial editions. VMware led the market in developing innovative features such as memory overcommitment, vMotion, Storage vMotion, Fault Tolerance, and more. Previously, VMware called their free hypervisor "Free ESXi" as ESXi Server is what is loaded directly on the physical server. However, VMware calls the "suite" of features "vSphere", available in various editions. Today, even the free hypervisor is called "The VMware vSphere Hypervisor". While the free vSphere hypervisor does have a graphical interface (the vSphere Client) and memory over-commitment, it doesn't offer features like vMotion, svMotion, high availability, or centralized management. The free version also has the limitation of supporting up to 32GB of RAM per physical server. The commercial versions of vSphere include features like:
Note: VMware vCenter, for centralized management (required for most advanced features) is sold separately
More information on VMware vSphere can be found here.