what is centos xen

In centos, Xen is an open source virtual machine monitor. It is an open source virtualization technology based on the The technology achieves high performance and can safely execute multiple virtual machines on a set of physical hardware.

#The operating environment of this tutorial: centos7 system, thinkpad t480 computer.

Xen is an open source virtual machine monitor developed by the University of Cambridge. It is intended to run up to 100 fully featured operating systems on a single computer. The operating system must be explicitly modified ("ported") to run on Xen (but to provide compatibility with user applications). This allows Xen to achieve high-performance virtualization without special hardware support.

Xen uses the ICA protocol to achieve high performance through a technology called paravirtualization. Even on some architectures (x86) that are extremely unfriendly to traditional virtualization technology, Xen also performs well. Unlike those traditional virtual machines that implement hardware through software simulation, Xen before version 3.0 with Intel VT-X support requires guest permissions on the system to connect to the Xen API. This technology is already available on NetBSD, GNU/Linux, FreeBSD and Plan 9 systems. Sun Microsystems is also actively porting Solaris to the Xen platform.

Xen virtual machines can be live migrated between multiple physical hosts without stopping. During operation, the virtual machine's memory is repeatedly copied to the target machine without stopping its work. Before the virtual machine starts executing at the final destination, there will be a very short pause of 60-300 milliseconds to perform final synchronization, giving a seamless migration feeling. A similar technique is used to pause a running virtual machine to disk and switch it to another, so that the first virtual machine can be resumed later.

XEN is an open source virtualization technology based on the X86 architecture with the fastest development, the most stable performance and the least resource usage. Xen can safely execute multiple virtual machines on a set of physical hardware. It is a perfect open source combination with Linux. Novell SUSE Linux Enterprise Server was the first to adopt XEN virtual technology. It is especially suitable for server application integration, which can effectively save operating costs, improve equipment utilization, and maximize the use of the IT infrastructure of the data center.

XEN is a virtualization open source project developed by the Computer Laboratory of the University of Cambridge in the UK. XEN can safely execute multiple virtual machines on a set of physical hardware. It is extremely closely integrated with the operating platform and consumes less resources. least. The stable version at the time of writing is XEN3.0. Supports universal virtualization and hyper-virtualization. Known for its high performance and low resource consumption, it has won high recognition and strong support from many world-class software and hardware manufacturers such as IBM, AMD, HP, Red Hat and Novell. It has been used by many domestic and foreign enterprises and institutions to build high-performance virtualization systems. platform.

IBM often uses virtual machines on its hosts and servers to maximize performance, and places programs in isolated virtual OSs like chroot imprisonment to enhance security. In addition to this, it enables different and incompatible OSs to run on the same computer. Xen's support for active migration of virtual machines allows for workload balancing and avoidance of downtime.

Comparison of Xen and other VMMs

Denali uses paravirtualization technology to improve the performance of virtual machines on x86 computers. Denali's virtual machine specifically supports a minimal operating system for Internet services. The system can run thousands of virtual machines. Xen differs from Denali in that it attempts to run a modest number of complete operating systems rather than a large number of lightweight operating systems.

VMware provides virtual machines for x86 that can run unmodified PC operating systems. The technology involved is extremely complex and results in a (sometimes quite significant) decrease in performance. Xen sacrifices full binary compatibility for relative simplicity and improved performance.

KVM performs better than Xen under full virtualization, but Xen is more efficient when running a modified operating system.

Platform support

Xen can run on x86, x86_64 and ARM systems, and is being ported to IA64 and PPC. Porting to other platforms is technically feasible and may be possible in the future.

Application fields

Xen has won more and more widespread applications due to its unique virtualization performance advantages. It is fully used by users in the following fields:

◆ Server application integration: Within the scope of the virtual machine, multiple servers are virtualized on one physical host to install multiple different applications and make full use of the physical capabilities of the server. performance and flexible server application migration.

◆Software development and testing: Users can use the low-cost advantage of Linux to build multiple application system development platforms very flexibly, thus saving a lot of development costs and speeding up the development process.

◆ Cluster computing: Compared with managing each physical host individually, virtual machine management is more flexible and easier to control and isolate in terms of load balancing.

◆Multi-operating system configuration: for the purpose of development and testing, run multiple operating systems at the same time;

◆ Kernel development: Do kernel testing and debugging in the virtual machine sandbox, without setting up a separate machine for testing;

◆ Provide hardware technical support for guest operating systems: New operating systems can be developed to benefit from the extensive hardware support of existing operating systems, such as Linux;

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