デュアルシステムDual System

Learn in the textbookSystem Configurations for Availability and Reliability

DefinitionA dual system (デュアルシステム) is a setup in which two systems carry out the same processing at the same time and compare the results to confirm they are correct.

ExplanationBoth systems handle live processing, so if the comparison turns up a mismatch, one of them has gone wrong. Running two full sets of equipment at all times is costly, but it suits work that demands high reliability.

AnalogyIt is like an accounts office where two clerks each total the same voucher and check every time that their answers agree.

Memory hook"Dual" means "two". Picture a swordsman with a sword in each hand, both blades in action.

Learn in the textbookReliability Design

DefinitionA dual system (デュアルシステム) runs the same processing on two systems at the same time and operates while comparing the results they produce.

ExplanationKeeping devices or systems in duplicate, spares included, so that a single failure does not stop the service is called a redundant configuration, and a dual system is one form of it. When the two results disagree, you know one side has gone wrong, so the system can even confirm that its processing is correct. Because both systems are always running, equipment and operating costs are high.

AnalogyIt is like two clerks each adding up the same invoice and checking their answers against each other before handing it in.

Memory hookDual means "both": both systems are always running the same processing.