Kernel-based Virtual Machine is an open source hypervisor solution (http://www.linux-kvm.org/page/Main_Page) for Linux that supports x86, PowerPC, and S390 CPU architecture that contains virtualization extensions. KVM uses the hardware virtualization support of these processors and effectively turns your Linux kernel into a bare metal hypervisor. It supports a mixed workload of various guest operating systems that run your applications on Linux and Windows in order to host critical and noncritical applications. Many current Linux distributions ship KVM and the Red-Hat-included KVM hypervisor technology in a release of Red Hat Enterprise Linux Version 5 update 4 and its later release.
KVM outperforms other virtualization hypervisors in various virtualization scenarios, and it has top scores in the SPECvirt_2010 virtualization benchmark. It includes the overall top performance scores and the highest number of performant VMs running on a single hypervisor. KVM is free software that was released under the GPL, and it's a powerful open source hypervisor solution alternative to the VMware, Citrix Xen, and Hyper-V RHEV overview.
The RHEV platform is an enterprise-grade, centralized-management hypervisor for server and desktop virtualization. It's a complete virtualization management solution that provides fully integrated management of your virtual infrastructures. The RHEV platform includes two major components: Red Hat Enterprise Virtualization Manager, which is a centralized management server, and optimized KVM hypervisor software, which hosts the virtual machines.
Red Hat supports RHEV through the subscription model, which provides enterprise-ready solutions that can be confidently deployed to manage even your most mission-critical applications. Red Hat subscription gives you access to the Red Hat customer portal (https://access.redhat.com) and provides simple, integrated access to all features of your subscription. Users can open support tickets, read and download the documentation, and find useful information in the knowledge base.
RHEV is based on the KVM hypervisor and the upstream oVirt open virtualization management platform, which is a project started by Red Hat and released to the open source community (http://www.ovirt.org/Home). oVirt is the community-supported open source project. It will be the baseline of RHEV products, and it's very similar to RHEL, which is based on the Fedora distro.