Virtual Server

Buzzword for the corporate and computer vendors, virtualization allows the use of processes specific hardware and software to run multiple Operating systems and applications on the same server, each in part completely independent. Each session is called virtual server and allows ultimately transform hardware into software. It is a solution totally server-based or terminals computer connected on a single computer.

In software, the VMware company remains pioneer and current leader. However, Microsoft announced in Option on Windows Server 2008, Sun and IBM is also developing solutions. At processors, AMD PACIFICA develops technology (AMD-V) for its Opteron since 2005, INTEL, VT-X technology. Both are optimized to facilitate operation of virtual machines (VM). This method has been used previously to emulate Windows on Mac computers to type (and thus the processor type X86) where even OS2 in its first version to run multiple sessions DOS Windows 3.x and totally independent.

Start by analyzing the interests, benefits and .. disadvantages. The first advantage is the use of a single optimum computer for a set of separate applications, without links to one another. This can use only one server running many more. The immediate disadvantage is the power required. Used server mode, interest is to run multiple systems operating simultaneously, such as Windows and Linux server. The solution proposed by Microsoft is rather like using a terminal.

This solution is being adopted by some companies, including large, although it can in theory reduce the number of network servers, and therefore the tasks of administration, power consumption, place and space, ....

1. Virtual machines.

In this mode, the server is managed by a standard Operating System. A virtual software to interface various systems sessions with separate operation, possibly different. The machine works like a hardware emulator for interfacing between Host operating systems and the global. This solution is generally heavy enough resources. This is for example the solution adopted on Macintosh to run Windows software.

It is the oldest method of virtualization. The most famous manager of this type is XEN.

2. Separation.

In this mode, a single operating system manages hardware, the Virtual Manager can completely isolate the different user sessions. This solution enables a crash of application to preserve the operation of the other.

It is also a security solution, virus or intrusion of a user session will not disturb others sessions. Using a more robust server, it allows client computers lower, when used in client - server mode. Interest is still limited, unlike costs of the stations being erased by the server. It is a work mode totally application dedicated.

3. Hypervisor mode.

The hypervisor mode emulates different operating systems on a system reduced operating specifically developed. The solution developed by Microsoft Windows Server 2008 but also allows for Linux example of using remote computers as mere terminals, even if the communication is Now with Ethernet or directly via VPN and the Internet link legacy applications via RS-232 serial connection. Less intensive CPU, it increases the data transfer the network. Again, the user sessions (operating system and applications) are completely dissociated.

4. Microprocessors.

These working methods all use of resources special software, but at the same processor (Including multi-core or even multi-processor). AMD (AMD-V) and Intel (VT-X) are developing solutions to optimize the virtual manager within the processor. These solutions do not replace the manager but improve it works as a manager of virtual machine (VM for short). This is needed for virtualisation fonction of Windows 7.

5. Internet, virtualized server.

This method is also used bu websites hosting, but in a different system. It between a dedicated and shared hosting, providing the benefits of a dedicated server for a lower price .. Many people are hosted by the same server (possibly several shared), y including bandwidth, such as a shared. By cons, each User manages its sites as a dedicated, including its sessions, websites, databases.

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