The computer facilities in the development on a way of speed increase of the PC has come nearer to physical limits. Time of electronic schemes switching has reached shares nsec., and speed of signals distribution in the lines connecting elements and units of the server, is limited by speed of light. Therefore the further reduction of time of nelectronic schemes switching will not allow to raise productivity of the server essentially.

Now exclusively the great value was got with a problem of high reliability maintenance of the computing systems working in structure of hardware systems various program. Especially at work of systems in a mode of real time to which systems virtual and dedicated hosting concern. This problem is solved by use of a redundancy principle which focuss on construction of multimachine systems. Occurrence of cheap and small microprocessors in the sizes and the PC has facilitated construction multimachine various purpose systems.

Realization of information interchange occurs, finally, by interaction of operational systems of servers among themselves. It worsens time characteristics of data exchange processes between servers. Application many server systems allows to raise reliability of computer complexes. At refusal in one server processing will be continued with other server of a complex. It allows to lead up server uptime to 100%. However thus the equipment of a complex can be used insufficiently effectively. There is enough in system in all servers to fail even on one device (even different types) as all system becomes disabled. A situation fantastic, but not impossible. For this reason we declare the servers uptime of 99,99 %.

That lack are deprived multiprocessing systems. In such systems processors find the status of ordinary units of the computing system, which similarly to other units, such as modules of memory, channels, peripheral devices, join in structure of system in the necessary quantity.

The computing system refers to multiprocessing if it contains some processors working with general RAM, and copes one general operating system. Often in MPS the general field of external memory will be organized.

As the general field it is understood equality of devices. The general field of memory means, that all modules OP are accessible to all processors and channels of input-output (or to all peripheral devices in case of presence of the general interface). General field means, that devices forming it are accessible to any processor and the channel.

In MPS in comparison with MSS faster information interchange between processors is reached. In fact linear distances in such system it is less, than in cluster system. More high efficiency both higher reliability and survivability Therefore can be received. Such system keeps working capacity while are efficient even on one module of each type of devices.

Multiprocessing systems represent the basic method of system ultrahigh productivity construction. And on the basis of multiprocessing and a modular principle of other devices construction of system probably creation completely failure-safe systems.

Construction of multiserver systems from serially let out PC with their standard operational systems is much easier, than construction of MPS demanding overcoming of certain difficulties, arising at realization of the memory general field, and, the main thing, labour-consuming development of special operating system.

Multiserver and multiprocessing systems can be homogeneous and non-uniform. Homogeneous systems contain same a server or processors. Non-uniform MSS consist of various type servers, and in non-uniform MPS various specialized processors, for example processors for operations from a floating comma, for processing decimal numbers, the processor realizing functions of operating system and the processor for matrix problems are used.

Multiprocessing systems and MSS can have single-level or hierarchical structure. It is usually less powerful PC (server-satellite) incurs input of the information from various terminals and its preliminary processing, unloading from these rather simple procedures the basic, more powerful COMPUTER, than the increase in the general productivity of a complex is reached. As satellites use a server of an initial level or PC.

The important structural feature considered systems is the way of the organization of communications between devices (modules) of system. It directly influences speed of information interchange between modules. Means from it productivity of system, speed of its reaction to inquiries and fitness to changes of a configuration depends. In particular, on the organization of intermodular communications depend frequency of occurrence of conflicts at the reference of processors to the same resources (first of all to modules of memory) and losses of productivity because of conflicts.

Next ways of the organization of intermodular communications are used:

• Regular communications between modules;
• The multilevel communications corresponding hierarchy of the PC interfaces;
• Multiport modules (in particular, modules of memory);
• The switch of intermodular communications
• The general trunk

Principles of the MPS organization and MSS essentially differ depending on their purpose. Therefore it is expedient to distinguish:

• systems, focused first of all on achievement of ultrahigh productivity;
• systems, focused first of all on increase of reliability and survivability, development and which designing we also are engaged.