問43
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業務用サーバの停電対策として導入予定の自家発電設備は，停電を感知してから安定した電源供給が得られるまでに1分かかる。その1分間のサーバ用電源を確保するために必要な装置はどれか。
平成22年度 春期 ITパスポート試験 問43
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This question's explanation and your answers so far.
解説
問 43
Incorrectア
An A/D converter (analog-to-digital converter) is a component that converts continuous analog signals such as sound or temperature into digital data a computer can handle. What it handles is signals, not electric power, and it has no function whatsoever for supplying electricity to a server during a power outage.
Incorrectイ
RAID is a redundancy technology that combines multiple magnetic disks and guards against disk failure through mirroring or parity. What it protects is data and the availability of storage devices; if power is lost, the disks stop along with everything else, so it does not secure electricity during an outage.
- ウ
正解 The correct answer is ウ, UPS. UPS stands for Uninterruptible Power Supply. It has a battery (storage battery) inside, and the moment the commercial power supply stops it automatically switches over to battery power and keeps supplying electricity to the connected equipment. The on-site power generator in this question takes 1 minute from detecting the outage until it delivers a stable supply, so unless electricity is supplied from somewhere during that 1 minute, the server goes down. The UPS acts exactly as the bridging power source that fills this gap: while the UPS battery holds things up, the on-site generator starts up, and this combination achieves non-stop operation. Note that the time a UPS can supply power is generally short, from a few minutes to a few tens of minutes, so for a long outage it is used together with an on-site generator, or a signal from the UPS is used to shut the server down safely and automatically.
Incorrectエ
A firewall is a security device or software that monitors and blocks communication at the boundary of a network to prevent unauthorized access from outside. The threat it addresses is a security threat, not a power outage, and it has nothing to do with power supply.
ここがポイント
- A UPS (Uninterruptible Power Supply) has a built-in battery and keeps supplying power to a server for about several minutes from the instant of an outage. It is introduced to fill the gap until an on-site generator becomes stable, or to buy time for a safe shutdown.
- In power-outage countermeasures, a UPS (a short-term bridge) and an on-site generator (a long-term alternative power source) share the roles between them. RAID, by contrast, is a countermeasure for disk failure, a firewall is a countermeasure for unauthorized access, and an A/D converter performs signal conversion — the question tests whether you can distinguish what each of them is meant to deal with.
用語