ITPEC IP April 2023 Question 14

Two computers perform exactly the same processing and cross-check the results — that is a dual system.

In a dual system both computers run the same job at the same time and collate their outputs, so an error shows up as a mismatch. If one computer fails, it is cut off and the other carries on with almost no interruption. This gives very high reliability, but because both do the same work, capacity is not increased.

Answer (a)

Why not others:

• •(b) — a primary system in normal use plus a secondary system on standby for a failure is a duplex system
• •(c) — computers connected as equals over a peer-to-peer network is horizontal distributed processing
• •(d) — computers in a clear hierarchy, such as a host computer with departmental servers and terminals below it, is vertical distributed processing

Key rule: Dual system = two systems doing the same work and comparing results; duplex system = one active system plus a standby that takes over after a failure.

System Component · AI-written, may contain errors