1.2. KVM and virtualization in Red Hat Enterprise Linux
(KVM) is a Full virtualization solution for Linux on AMD64 and Intel 64 hardware. KVM is a Linux kernel module built for the standard Red Hat Enterprise Linux 6 kernel. KVM can run multiple, unmodified virtualized guest Windows and Linux operating systems.The KVM hypervisor in Red Hat Enterprise Linux is managed with the libvirt API and tools built for libvirt, virt-manager and virsh. Virtualized guests are run as Linux processes and threads which are controlled by these modules.
Red Hat Enterprise Linux KVM hypervisors can be managed by the Red Hat Enterprise Virtualization Manager as an alternative to the virsh and virt-manager tools.
The kvm package also contains Linux kernel modules which manage devices, memory and management APIs for the Hypervisor module itself.
This book covers virtualization topics for Red Hat Enterprise Linux 6. The Kernel based Virtual Machine (KVM) hypervisor is provided with Red Hat Enterprise Linux. The KVM hypervisor supports Full virtualization.
The KVM hypervisor supports overcommitting virtualized CPUs and memory. Overcommitting means allocating more virtualized CPUs or memory than the available resources on the system. CPU overcommitting allows virtualized guests to run on fewer servers and in higher densities. Memory overcommitting allows hosts to utilize memory and virtual memory to increase guest densities.
Kernel SamePage Merging (KSM) is used by the KVM hypervisor to allow KVM guests to share identical memory pages. These shared pages are usually common libraries or other identical, high-use data. KSM allows for greater guest density of identical or similar guest operating systems by avoiding memory duplication.
