the same scheduler as on the host, allowing guest's processes to run concurrently on SMP systems. This is not trivial to implement with whole-system emulation. Networking is based on isolation rather than virtualization, so there is no additional overhead for packets. Smaller plane for security bugs. Only one kernel with small additional code-base compared to 2+ kernels and large interfaces between them. Rich Linux scheduling features such as real-time priorities. Disadvantages Requires that the host kernel be patched. No clustering or process migration capability is included, so the host kernel and host computer is still a single point of failure for all virtual servers. Networking is based on isolation, not virtualization. This prevents each virtual server from creating its own internal routing or firewalling setup. Some system calls (mostly hardware-related: e.g. real-time clock) and parts of the /proc and /sys filesystems are left unvirtualized. Does not allow disk I/O bandwidth to be allocated on a per-virtual server basis. See also Comparison of platform virtualization software Operating system-level virtualization References External links Official releases Implementation paper Linux security software Linux kernel features Free virtualization software Linux-only free software Virtualization software for Linux