Xen is an open source Virtual Machine Monitor (VMM) originally developed by the Systems Research Group of the University of Cambridge Computer Laboratory, as part of the UK-EPSRC funded XenoServers project.
Xen can securely execute multiple virtual machines, each running its own operating system, on a single physical system with close-to-native performance.
The Xen Cloud Platform addresses the needs of cloud providers, hosting services and data centers by combining the isolation and multitenancy capabilities of the Xen hypervisor with enhanced security, storage, and network virtualization technologies.
- Small footprint and interface. Xen uses a microkernel design, with a small memory footprint and limited interface to the guest.
- Operating system agnostic.
- Driver Isolation: Xen has the capability to allow the main device driver for a system to run inside of a virtual machine. If the driver crashes, or is compromised, the VM containing the driver can be rebooted and the driver restarted without affecting the rest of the system.
- Paravirtualization: Fully paravirtualized guests have been optimized to run as a virtual machine. This allows the guests to run much faster than with hardware extensions (HVM). Additionally, Xen can run on hardware that does not support virtualization extensions.
- Advanced Memory Management:
- Memory Ballooning.
- Memory Sharing.
- Memory Paging.
- Resource Management:
- Credit 2 Scheduler (experimental).
- NUMA scheduler affinity.
- 1GB/2MB super page support.
- Deliver events to PVHVM guests using Xen event channels.
- Interoperability / Hardware support:
- Nested Virtualisation (experimental).
- HVM PXE Stack.
- Physical CPU Hotplug.
- Physical Memory Hotplug.
- Support for PV kernels in bzImage format.
- PCI Passthrough.
- X86 Advanced Vector eXtension (AVX).
- High Availability and Fault Tolerance:
- Live Migration, Save & Restore.
- Remus Fault Tolerance.
- Network and Storage:
- Online resize of virtual disks.
- Driver Domains.
- Device Model Stub Domains.
- Memaccess API.
- XSM & FLASK.
- XSM & FLASK support for IS_PRIV.
- vTPM Support.
- Serial console.
- Device Models and Virtual Firmware for HVM guests:
- Traditional Device Model.
- Qemu Upstream Device Model.
- OVMF/Tianocore (experimental).
- PV Bootloader support:
- PyGrub support for GRUB 2.
- PyGrub support for /boot on ext4.
- pvnetboot support.
- NUMA scheduling affinity.
- Openvswitch integration.
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