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一、（用戶空間）軟件級別虛擬化（OS級別虛擬化） 1、vmware workstation 2、openVZ 特點(diǎn)： 1、只能實(shí)現(xiàn)完全虛擬化,一般情況下一個虛擬機(jī)就是操作系統(tǒng)上面的一個進(jìn)程，虛擬化軟件控制資源的能力低下 2、虛擬機(jī)的所設(shè)備都由應(yīng)用層軟件來模擬,虛擬機(jī)中看到的所有硬件都是假的，指令集轉(zhuǎn)換的路徑過長，所以效率低下，一般不于企業(yè)環(huán)境 3、實(shí)現(xiàn)起來簡便，可以造假，一般叫超載或者叫超賣 （內(nèi)核空間）內(nèi)核級別虛擬化（OS級別虛擬化） KVM 特點(diǎn)： 1、只能實(shí)現(xiàn)完全虛擬化，功能完善 2、虛擬機(jī)的所有設(shè)備都由應(yīng)用層軟件來模擬，效率比軟件級別虛擬化較強(qiáng)，因?yàn)檗D(zhuǎn)換路徑比用戶空間虛擬短,另外虛擬化軟件運(yùn)行在操作系統(tǒng)的核心之上，所以對資源的控制能力也比較強(qiáng)。 （底層）hpyervisor虛擬化 1、xen 2、vmware ESX 3、微軟hpyervior 特點(diǎn)： 1、hpyervisor直接運(yùn)行在硬件之上，對硬件（CPU、MEMORY，中斷）絕對的控制權(quán)，效率強(qiáng)勁 2、需要一個domain0來管理除CPU、MEMEORY、中斷以外的硬件處理 3、實(shí)現(xiàn)半虛擬化時需要修客戶機(jī)內(nèi)核，實(shí)現(xiàn)比較麻煩，裝好軟件后需要重啟機(jī)器 4、可以實(shí)現(xiàn)半虛擬化或者全虛擬化，需要CPU配合。 二、虛擬機(jī)分類： 完全虛擬化(不需要更改操作系統(tǒng)的內(nèi)核，所有的硬件都靠軟件來模擬，所以硬件都是假，另外虛擬機(jī)的硬件工作時指令集都需要轉(zhuǎn)換) 半虛擬化（需要更改母機(jī)和虛擬機(jī)的內(nèi)核，一般不需要軟件來模擬，直接使用物理） XEN的邏輯結(jié)構(gòu)： XEN結(jié)構(gòu)邏輯圖 Below is a diagram of the Xen architecture. The Xen hypervisor runs directly on the hardware and is responsible for handling CPU, Memory, and interrupts. It is the first program running after exiting the bootloader. On top of Xen run a number of virtual machines. A running instance of a virtual machine in Xen is called a domain or guest. A special domain, called domain 0 contains the drivers for all the devices in the system. Domain 0 also contains a control stack to manage virtual machine creation, destruction, and configuration. Components in detail: The Xen Hypervisor is an exceptionally lean (<150,000 lines="" of="" code)="" software="" layer="" that="" runs="" directly="" on="" the="" hardware="" and="" is="" responsible="" for="" managing="" cpu,="" memory,="" and="" interrupts.="" it="" is="" the="" first="" program="" running="" after="" the="" bootloader="" exits.="" the="" hypervisor="" itself="" has="" no="" knowledge="" of="" i/o="" functions="" such="" as="" networking="" and=""> Guest Domains/Virtual Machines are virtualized environments, each running their own operating system and applications. Xen supports two different virtualization modes: Paravirtualization (PV) and Hardware-assisted or Full Virtualization (HVM). Both guest types can be used at the same time on a single Xen system. It is also possible to use techniques used for Paravirtualization in an HVM guest: essentially creating a continuum between PV and HVM. This approach is called PV on HVM. Xen guests are totally isolated from the hardware: in other words, they have no privilege to access hardware or I/O functionality. Thus, they are also called unprivileged domain (or DomU). The Control Domain (or Domain 0) is a specialized Virtual Machine that 0 has special privileges like the capability to access the hardware directly, handles all access to the system’s I/O functions and interacts with the the other Virtual Machines. It also exposes a control interface to the outside world, through which the system is controlled. The Xen hypervisor is not usable without Domain 0, which is the first VM started by the system. Toolstack and Console: Domain 0 contains a control stack (also called Toolstack) that allows a user to manage virtual machine creation, destruction, and configuration. The toolstack exposes an interface that is either driven by a command line console, by a graphical interface or by a cloud orchestration stack such as OpenStack or CloudStack. Xen-enabled operating systems: A Xen Domain 0 requires a Xen-enabled kernel. Paravirtualized guests require a PV-enabled kernel. Linux distributions that are based on recent Linux kernel are Xen-enabled and usually contain packages that contain the Xen Hypervisor and Tools Xen (the default Toolstack and Console). All but legacy Linux kernels are PV-enabled: in other words, they will run Xen PV guests. XEN結(jié)構(gòu)邏輯圖 XEN結(jié)構(gòu)邏輯圖 KVM的邏輯結(jié)構(gòu)圖： KVM結(jié)構(gòu)邏輯圖 |
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