Server Selection Criteria

Below we list—non-exhaustively—selection criteria appropriate for an IT professional to use in choosing a server, following the list by a discussion of each criterion in turn:

• Availability of applications and development tools
• System availability
• Data integrity
• Security
• Performance
• Scalability
• Price
• Support for the client/server model
• Architectural maturity
• Investment risk

Note that the list is given in no particular order; when selecting a server, the individual needs of the business will drive the relative weighting of the criteria.

The availability of a vast catalogue of applications and development tools eases the construction of business solutions and is an indication that the server family under consideration has a strong and active marketplace. Such an active market has beneficial indirect effects: reduced prices because of volume and competitive effects; enhanced confidence in the continuity of the vendor and platform; widespread availability of experts in the applications and the tools. We should note in passing that the success of a platform is rarely an effect of the intrinsic merits of its technology (whether hardware or software); it is the marketplace that decides.

Since business activities rely more and more on their data processing resources, three criteria of increasing importance are availability, data integrity, and security. By availability, we mean the ability of the system to perform its function every time that it is requested; integrity corresponds to the system’s ability to manage its data without damage to the data; and security is the ability to ensure that there is no unauthorized access to that data.

The performance of a system is an important characteristic, but it is difficult to characterize with a single number. The best way of capturing performance is to identify what the system must do to fulfill its mission and then identify the values that allow one to characterize performance for that mission. If the analysis of the workload shows that one or more standard benchmarks is a close approximation to the workload, then one may use the relative performance of different systems on the relevant benchmark(s) to provide a good predictor of performance on the company’s workload. If no benchmarks fit well, then one can compare performance only by running tests on the real workload. Since systems needs often change over time, it is generally a good idea to leave some "headroom" in available performance when choosing a system.

Scalability—the ability of a system to match the dimensions of the problem it has to manage—is closely related to performance. But given the choice of two systems, one may prefer a less powerful system with good scalability over a more powerful system with less growth potential.

Over the course of time, the ways of comparing price have changed, shifting from a simple price comparison of the systems under consideration (both hardware and software) with support and maintenance costs added in, to a “Total Cost of Ownership” approach, which also integrates internal costs, such as the staff needed to operate the system, system management and user support costs, the economic impact on the company were the system to become unavailable, etc.

Support for the client/server model depends on the availability of appropriate middleware; some platforms are better served than others in this area. For example, standard systems present a significant potential market, and so attract the attention of middleware publishers.

Although the various concepts used in server architectures are widely known, the development of a new architecture often takes longer than originally expected by its developers. The various aspects of maturity are very powerful forces; one such effect is the difficulties innovative architectures often meet while going to market.

Installing a server and the necessary applications represents a major investment, in terms of both immediate expenditure (acquisition costs of hardware and software) and associated costs (training, implementing new applications, etc.). Given the usual size of these costs, the investment risk is an important criterion. It is particularly important that a server vendor stay in existence for as long as its customers are using its products, and so this issue presents a particular problem to start-ups, since so many collapse while young. This difficulty can be less severe for suppliers of products like storage subsystems, since these have extremely well defined interfaces with their host systems—so, if the supplier collapses, all is not lost—alternative products from other vendors can be deployed in the same way and with the same connections as the products from the ill-fated start-up. In general, however, the subsystems purchased from the defunct vendor must be replaced, since such subsystems will, in general, only run software provided by their vendor.

Source of Information :  Elsevier Server Architectures 2005


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