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Remember XenServer, one of the three major virtualization te

Introduction: XenServer is an open source project and community initiated and managed by Citrix. The open source software developed by the project implements multiple functions of virtualization, allowing multiple operating systems and applications to be safely run on hardware devices, completing hardware integration and automation; transforming static, complex IT environments into more dynamic and easy Managed virtual data centers.

Foreword

XenServer is an open source project and community initiated and managed by Citrix. The open source software developed by the project implements multiple functions of virtualization, allowing multiple operating systems and applications to be safely run on hardware devices, completing hardware integration and automation; transforming static, complex IT environments into more dynamic and easy Managed virtual data centers, effectively reducing IT resource costs, providing advanced management capabilities, enabling virtual data center integration and automation, simplifying server and application management.

XenServer Development

Xen originally originated from a research project at the University of Cambridge "XenoServer-wide computing project", led by Ian Pratt, a senior lecturer at Cambridge University, and later with Simon of Cambridge University Crosby co-founded Xensource.

Xen's initial public offering was in 2003.

In 2004, shortly after the release of Xen 2.0, Ian Pratt and several other technology leaders set up Xensource to upgrade the Xen hypervisor from a research tool to a competitive enterprise computing product. As part of the company's strategy, the Xen hypervisor remains an open source solution.

In 2005, the xen hypervisor was widely adopted, and Red Hat, Novell, and Sun all added the Xen hypervisor to their virtualization solution. In the same year, the xen hypervisor was widely adopted, and Red Hat, Novell, and Sun all added the Xen hypervisor to their virtualization solution. The development community also passed the Xen 3.0 versionThis speeds up the functionality of Xen. Microsoft and VMware also adopted the paravirtualization concept first introduced by the Xen community.

In 2006, the release of XenServer 3.1 broke the limitation of Xen virtual machine only to Linux. Through the hardware features of Intel VT and AMD-V, the support of Windows virtual machine was realized.

On October 22, 2007, Citrix Systems completed the acquisition of Xensource and publicized the existence of the Xen Project Advisory Committee (Xen AB) from Citrix, IBM, Intel, Hewlett-Packard , Novell, Red Hat, Sun Microsystems, and Oracle. Shortly before the acquisition by Citrix, XenSource released XenEnterprise v4, introducing a new cluster management component XAPI toolset and a brand new based. NET's interface management tool XenCenter, a commercial product that introduces XenSource into the Enterprise version. After the acquisition of Citrix, its products were consolidated and renamed to XenServer.

In 2009, XenServer 5.5.0 was released with features including consolidated backups, enhanced search tools, integration with Active Directory, and greater support for operating systems such as Windows and Linux. Laid the position of Citrix in the server virtualization market. Subsequent versions continue to enrich various aspects of virtualization technology, such as online live migration, automatic recovery, and the use of ovs as the default network management tool, enhancing support for computing, storage, networking, and guest operating systems.

On April 15, 2013, the Xen project was announced as a collaborative project to move to the Linux Foundation. The Linux Foundation has introduced a new "Xen project" to distinguish it from the old "Xen". On June 24, 2013, Citrix announced the open source XenServer project with the goal of using its previous proprietary XenServer as aOpen source products are delivered to the open source community for more input and participation.

In January 2015, XenServer 6.5 released, based on 64-bit CentOS 5.10 control domain, using Xen hypervisor v4.4, improved network, storage and vGPU features and performance . This is a more widely used version.

Currently, the XenServer version has been released to version 7.6.

XenServer Architecture

The above picture shows the architecture of Xen. The Xen hypervisor runs directly on physical hardware and handles tasks related to CPU, memory, timers, and interrupts. After the system completes the bootloader, the Xen hypervisor starts first.

On top of the Xen hypervisor, there are multiple virtual machines running. These virtual machines running instances are called domains or guests in Xen. The most special domain is called Domain 0 or VM 0. This is a control domain, referred to as Dom0, as shown on the left side of the figure. Domain 0 removes all the drivers that contain the corresponding system devices, as well as a control stack and various system services for managing Xen-based systems. Through the Domain 0 decomposition, some services and device drivers in Domain 0 can be removed and run in a dedicated virtual machine, which requires some special configuration.

Xen hypervisor: The Xen hypervisor is a very thin software layer (<65ksloc on ARM, <300ksloc on x86) that runs directly on the hardware and manages CPU, memory and interrupts. It is the first program that runs after the boot loader exits. The hypervisor itself does not handle I/O functions such as networking and storage.

Guest Domain: Alias ​​DomU, which is a virtualized environment for real business, each running its own operating system and applications. The hypervisor supports several different virtualization modes, and the Guest Domain is completely isolated from the hardware.In other words, they don't have the privilege to access hardware or I/O functions. Therefore, they are also called unprivileged domains (DomU).

Control Domain(Domain 0): alias Dom0, which is a special virtual machine with special privileges, such as direct access to hardware, handling of all access to system I/O functions, and interaction with other virtual machines. Ability. Without Dom0 (the first virtual machine booted by the system), the Xen hypervisor cannot be used. In the standard settings, Dom0 includes the following functions:

System Services: such as xenstore / xenbus (XS) for managing parameters, Toolstack Toolset (TS) for exposing user interfaces to virtual machines, Qemu-based devices Simulation (DE) service.

Native device driver: Dom0 manages physical device drivers, so native hardware support for Xen systems is supported.

Virtual Device Driver: Dom0 removes physical device drivers and also supports virtual device drivers, also known as backends.

Tool Set: Allows users to manage the creation, deletion, and modification of virtual machines. The functional interfaces provided by the toolset can be called from the command line, graphical interface, or through third-party cloud management platforms, such as openstack and cloudstack. A variety of different toolsets can be used with Xen.

Xen Project-enabled operating systems: Dom0 requires a valid kernel. Xen projects are supported on Linux distributions based on kernels that are newer than Linux 3.0, and typically include packages that include hypervisors and tools (the default toolset and console).

XenServer basic concept

in the virtualization service provided by xen, abstract different objects in multiple concepts in computing, network, and storage, so as to effectively manage logically, isolate specific Implementation and operation, allowing users to focus more on business logic and use cases.

The above figure lists the main data objects and relationships in Xen. You can use the command line to interface XenCent.Er and XAPI operate to implement various related functions of computing, storage, and networking. The main objects mapped to the function are as shown in the figure below, and the virtual machine and the Xen server are connected from the network and the storage function lines.

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