KVM is a relatively small piece of code, leveraging Linux for much functionality. This makes KVM easy to secure and very flexible in meeting future needs.
Leveraging Linux means that KVM automatically gains the power of Linux’s hardware support, memory management, network utilities, cgroups, SELinux, etc.
Features: RHEL6.3 KVM has all the features of modern hypervisors, without needing 3rd party tools: live snapshots, virtualized disk drivers (VIRTIO), live migration, live block migration, USB passthrough, guest power management, etc.
Performance: RHEL 6.3 + KVM holds the top 7 SPECvirt spots on HP and IBM hardware, with metrics showing ~20%+ better performance than VMWare.
Single Guest Scalability: Now supports 160 vCPUs and 2TB RAM per guest (with no additional licensing costs!)
RHEL 7.0 will include virtual PCI bridges and will have a new Virtio-SCSI block device, enabling thousands of devices per virtual machine.