問47
頻出度★★★
無停止のシステムを実現するために, システムの方式を設計するときの検討事項として, 適切なものはどれか。
平成25年度 秋期 ITパスポート試験 問47
テクノロジ系システム構成要素 › システムの評価指標
This question's explanation and your answers so far.
解説
問 47
Incorrectア
Modularization of software into components is a design technique for improving reusability, maintainability and development productivity. Even if the software is split into components, if only one machine runs that processing the system still stops when it fails, so this is not a direct means of achieving non-stop operation (higher availability).
Incorrectイ
Encryption of data is a confidentiality measure that prevents eavesdropping and information leakage. It works on confidentiality among the three elements of information security, not on availability, which is what prevents the system from stopping due to equipment failure.
Incorrectウ
Power-saving design of hardware is a measure for reducing power consumption, running costs and environmental load. Lowering power consumption does not prevent failures themselves, nor does it create a mechanism to take over processing when a failure occurs, so it does not directly lead to non-stop operation.
- エ
正解 The correct answer is エ, redundancy (multiplexing) of hardware. A non-stop system is a system that keeps providing service even when a failure occurs. If it is built from only a single unit of equipment, the whole system stops the moment that one unit breaks (a single point of failure). Therefore CPUs, disks, power supplies, network devices and so on are duplicated or multiplexed, so that when one of them fails the remaining ones take over the processing. This is redundancy (multiplexing), and the dual system, duplex systems such as hot standby, and fault-tolerant design are all based on this idea. Hence, the appropriate consideration for achieving non-stop operation at the stage of designing the system configuration is redundancy (multiplexing) of hardware.
ここがポイント
- The basic measure for a non-stop system (high availability) is redundancy, that is, multiplexing of hardware. Preparing standby equipment and switching over on failure eliminates the single point of failure (dual system, hot standby, fault tolerant).
- Organized by the three elements of information security: encryption is a measure for confidentiality, while multiplexing and backup are measures for availability. Whether the question asks about keeping the system running or about protecting information changes which measure you should choose.
用語