問56
頻出度★★★
ホットスタンバイ方式の説明として, 適切なものはどれか。
平成26年度 春期 ITパスポート試験 問56
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 56
Incorrectア
“Providing users with a collection of diverse hardware, software, and data available on the Internet” is a description of cloud computing, which is a different concept from system duplexing and reliability design. Hot standby is about an organization's own system configuration (the active system and the standby system), so this is wrong.
Incorrectイ
“Running two machines simultaneously, always performing the same processing and mutually checking the results” is a description of a dual system. In a dual system both lines execute the same processing at the same time and compare the results, which makes it strong at error detection; in hot standby, however, the standby system does not run the same business processing in parallel — it simply waits. They are different methods.
- ウ
正解 The correct answer is ウ. The hot standby method is a duplexing (redundancy) approach in which the backup machine (the standby system) is kept waiting in a “ready to operate at any time” state — already powered on and with the system already started — so that the moment the production machine (the active system) fails, processing is automatically taken over by the backup machine. The standby system normally does not perform the actual work (or waits while receiving replicated data from the active system), but because no start-up work is needed, the switchover time is extremely short and the system's operating rate (availability) can be kept high. Choice ウ, “a method that keeps a backup machine on standby in a ready-to-operate state at all times, and switches to it immediately when a failure occurs,” is exactly this definition.
Incorrectエ
“When a failure occurs, an operations staff member starts the backup machine and switches over” is a description of cold standby. The backup machine is normally powered off, and start-up, environment configuration, and data recovery work are required, so the switchover takes time. This differs from hot standby, which “switches over immediately,” in the immediacy of the switchover, so it is wrong.
ここがポイント
- Distinguishing the system duplexing methods: hot standby (the standby system waits in a started-up state and switches over automatically and immediately on failure) / warm standby (the standby system is started up but still needs some preparation) / cold standby (the standby system is stopped and must be started manually before switching over on failure).
- The difference between a dual system and a duplex system: a dual system is a method in which two lines perform the same processing at the same time and compare the results, while a duplex system (hot standby and cold standby are forms of it) separates the roles into an active system and a standby system and switches to the standby system when a failure occurs.
用語