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System Architecture and Reliability

Which describes a dual system?

  1. AA primary (active) system and a standby system are provided; normally only the primary processes, and when the primary fails, processing switches to the standby and continues
  2. BSeveral systems share the processing to raise the overall capacity
  3. CTwo systems perform the same processing at the same time and compare the results, and if one fails, the other continues processing
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Answer: C. Two systems perform the same processing at the same time and compare the results, and if one fails, the other continues processing

A dual system runs the same processing on two systems at the same time and compares the results as it operates. If the results disagree, an error can be noticed, and if one system fails the other can continue processing as is, so it is used for processing that requires high reliability. In exchange, the cost is high because two sets of equipment do the same work. Dividing into a primary and a standby and switching over on failure is a duplex system.

  • A. This describes a duplex system.
  • B. This describes load sharing. The two systems do not perform and compare the same processing.
  • C. Correct. The same processing is performed at the same time and the results are compared.
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More System Architecture and Reliability questions

  1. The servers of a semiconductor fab's manufacturing execution system (MES) are made a duplex system consisting of a primary (active) system and a standby system. Which is a characteristic when the standby system is a hot standby?
  2. A system has two redundant load balancers, three web servers behind them, and a single database server used by all the web servers. Among the devices listed here, which is a single point of failure (a point whose stopping stops the whole system)?
  3. A cluster in an active-active configuration shares processing evenly among five servers. Utilization is proportional to the amount of processing. The goal is to keep each server's utilization at 80% or less even when one server fails and the remaining four take over its processing evenly. Which is the upper limit of each server's utilization in normal operation (all five running)?
  4. A system uses three servers with an availability of 0.95 each and has the required capacity as long as at least two of them are running. The servers fail independently, and failures of devices other than the servers are ignored. Which is the availability of this system?
  5. Which is an example of a design based on the fail-soft concept?