Mainframe era
When the earliest mainframe appeared, the price was relatively expensive and the computing power of the whole mainframe was relatively high. At that time, some people put forward the method of using one machine by multiple users, but it was not a real desktop virtualization, but a multi-tasking form that relied on multiple users of the system. For example, server versions of LINUX, UNIX, and WINDOWS can support multi-user forms.
Hard disk partition under WINDOWS
This may have to be mentioned. This is definitely not a virtualization category, but it must be mentioned. With the increasing capacity of hard disk, we logically divide the hard disk into different areas for different purposes, which is somewhat similar to the "virtualization technology" of hard disk.
Founder of desktop virtualization protocol.
The RDP/ICA protocol, as people in the industry may know, was developed after Microsoft bought it from CITRIX. RDP is the most popular remote desktop protocol in the past and now, so RDP and ICA are brothers, but they are put forward by different manufacturers, so they are naturally different.
* * * Enjoy the device
For many users, the hedonist is also quite familiar. The server carries the operating system and distributes it to the end users remotely through the Microsoft protocol. End users only need a very simple box to get the desktop. Desktop virtualization and desktop protocols look very similar, but they are not brothers. Desktop virtualization is a server that hosts multiple systems and distributes them to end users through proprietary desktop protocols. These two differences determine the different positioning of the two products, and the hedonist has been in the market for a while and then gradually withdrew from the market.
Desktop operating system virtualization
The theme here is to distinguish server virtualization technologies, with special emphasis on virtualized desktop operating systems. In fact, this concept can be basically equivalent to the desktop operating system implemented by Vmware Workstation and Microsoft VPC. Of course, this application mode is often used by developers and testers, although the virtual desktop system is not necessarily XP, 2000 professional, vista, etc. This is mentioned here because when virtualization technology just emerged, some manufacturers defined it as desktop virtualization technology. For example, before Microsoft introduced MED-v technology, VPC was defined as Microsoft's desktop virtualization product.
The so-called desktop virtualization defined by this perspective can basically be regarded as a virtualization solution for desktop systems on PCs, but it has a simple difference and correspondence with server virtualization. Its own solution is still the separation of installation environment and operating system running environment, which does not depend on specific hardware. However, it is undeniable that the real virtual desktop technology began to appear after the server virtualization technology matured.
The first generation desktop virtualization technology
The first generation of desktop virtualization technology really combines the remote access ability of remote desktop with virtual operating system, which makes the enterprise application of desktop virtualization possible.
First of all, with the maturity of server virtualization technology and the enhancement of server computing power, the server can provide the computing power of multiple desktop operating systems. Take Zhiqiang processor 16G memory server with 4 cores and dual CPU as an example. If the user's xp system allocates 256M memory, a server can support 50-60 desktops on average. It can be seen that if desktops are provided by virtual desktops, the procurement cost of 50-60 desktops will be higher than that of servers, and the management cost and security factors have not been counted, so the emergence of server virtualization technology makes it possible for enterprises to apply desktop virtualization technology on a large scale.
Of course, if you just turn the operating system running on the desktop into a virtual machine running on the server, users will not be able to access it and will certainly not be accepted by anyone. Therefore, the core and key of virtual desktop is not desktop virtualization in the background server virtualization technology, but the ability to enable users to access their desktops at any time and any place through various means, that is, remote network access. And this goes back to the same point of application virtualization, that is, the efficiency of remote access protocol.
The main vendors providing desktop virtualization solutions are Microsoft, Vmware and Citrix, and the remote access protocols used mainly use three protocols: RDP protocol, which was developed by Citrix in the early days and later acquired by Microsoft and integrated into Windows, used by Microsoft desktop virtualization products, and also used by hardware products such as Sun Ray based on VMware; The second is the unique ICA protocol developed by Citrix itself, which Citrix uses in its application virtualization products and desktop virtualization products. Thirdly, the PCoIP protocol developed by Teradici Company in Canada is used in VMware's desktop virtualization products to provide high-quality virtual desktop user experience.
Protocol efficiency determines the user experience of virtual desktop, and user experience is the key to the vitality of desktop products (both the success of Microsoft and the decline of Vista have proved this). According to official documents and actual tests, ICA protocol is usually superior to RDP and PCoIP protocol, and requires a bandwidth of 30-40kbps, while RDP is at 60kbps, which does not include the bandwidth occupation when watching videos, playing games and 3D drawing. Because of this difference, the user experience of virtual desktop is also very different. Generally speaking, in the local area network environment, general RDP and ICA applications can run normally, but RDP protocol occupies a large number of networks, but it has no great impact on performance. However, RDP protocol is basically unavailable in WAN or even Internet. In applications such as video viewing, Flash playback and 3D design, even the performance of RDP will be greatly affected (there are many videos to compare on Youku), and the user experience of ICA will be smooth. Moreover, according to the introduction of HDX just launched by Citrix, the promotion of new technologies in this area will be faster. Microsoft and Vmware are also aware of this difference. Microsoft turned to increase the research and development and optimization of RDP protocol, and VMware also cooperated with Teradici Company of Canada to provide high-quality virtual desktop user experience by using its PCoIP protocol. The latest VMware view 5.0 product improves the performance of PCoIP protocol and reduces the bandwidth utilization by 75%, which is also the leading protocol for virtual desktop.
In particular, Microsoft uses Hyper-v, Vmware uses its own vSphere, and Citrix can use XenServer, Hyper-v and vSphere as server virtualization technologies in the background of these three vendors.
The second generation desktop virtualization technology
The first generation technology realizes the combination of remote operation and virtual technology. The popularization of virtual desktop technology is possible because of the reduction of cost, but it affects not only the procurement cost, but also the management cost and efficiency.
Looking at the history of IT technology application, the change of architecture is the same as the famous saying of the Three Kingdoms: long-term separation must be combined, long-term separation must be separated. From the earliest centralized mode of host-terminal, to the distributed mode of PC, and then to today's virtual desktop mode, it is actually a game development that calculates the right to use and manage. Start the host mode, centralized management, but the application is difficult, you must go to the computer room to use; With the advent of the PC era, all computing takes place on the PC, but the management of IT has also become distributed, which is why the desktop administrators in IT departments are under the greatest pressure. They need to manage all users' PCs in a distributed manner, and the management cost has also increased greatly. Desktop virtualization separates the user's running environment from the actual running environment of the system, and IT is not necessary to be in one place at the same time, which not only satisfies the flexible use of users, but also helps IT departments to realize centralized control, thus solving this problem. However, if only 65,438+10,000 employees' PCs are replaced by 65,438+10,000 virtual machines, the management pressure of IT administrators will not necessarily decrease, but will increase, just without running around.
In order to improve manageability, the second generation desktop virtualization technology further separates the running environment and installation environment of the desktop system, applications from the desktop and configuration files, which greatly reduces the complexity and cost of management and improves management efficiency. As shown in the figure below:
Let's do a simple calculation: if an enterprise has 200 users, IT administrators need to manage 200 images (including installed applications and configuration files) without splitting them. However, if the operating system is installed and the application and configuration file are split, assuming there are 20 applications, the administrator only needs to manage the 20 applications by using application virtualization technology without installing the applications on the desktop. Configuration files can also use the built-in functions of Windows, and the file data is saved on the file server, which does not need administrator management, and the administrator only needs to manage one file server. However, applications and configuration files are separated. The operating systems of 200 people are all Windows XP, and administrators only need to manage one image (using this image to generate 200 running virtual operating systems can be simply understood as a model similar to a diskless workstation). So generally speaking, IT administrators only need to manage 20 applications, 1 file server and 1 image. Management complexity is greatly reduced.
This split also greatly reduces the demand for storage (199 xp less storage) and reduces the procurement and maintenance costs. More importantly, in terms of management efficiency, administrators only need to patch or upgrade an image or an application, and all users will get the latest update results, thus improving the security and stability of the system and greatly reducing the workload.