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System Architecture and Reliability

Learn system architecture and reliability with multiple-choice questions: system configurations such as client-server and three-tier systems, dual and duplex systems and hot standby, RAID capacity and tolerated failures, full, differential and incremental backups with RPO and RTO, fail-safe, fail-soft and fool-proof design, cloud and virtualization, SAN and NAS, PUE, and capacity planning.

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System Architecture and Reliability: key points

How usable and how hard to stop an information system is depends not only on the performance of one computer but on how equipment is combined and how processing continues when something fails. This design matters especially for systems whose stopping directly affects production, such as a semiconductor fab's manufacturing execution system (MES) and the servers that collect equipment data.

This topic covers system configurations such as client-server, three-tier client-server, peer-to-peer, and batch and online processing, and redundancy concepts such as dual and duplex systems, hot standby, clusters and single points of failure. It also covers, with calculation questions, RAID capacity and the number of failures each level tolerates, backup restore procedures, RPO and RTO, reliability design such as fail-safe, IaaS, PaaS and SaaS, live migration, SAN and NAS, PUE and UPS, and estimating the number of servers needed. It also helps with the system components sections of IT certification exams such as Japan's Fundamental and Applied Information Technology Engineer Examinations.

All System Architecture and Reliability questions (40)
  1. Which describes a client-server system?
  2. In a three-tier client-server system, which tier handles the business processing (business logic)?
  3. Which describes a thin client?
  4. Which is a characteristic of a peer-to-peer (P2P) system?
  5. Which is a characteristic of distributed processing compared with centralized processing?
  6. Which task is suited to batch processing?
  7. Among the measures used to evaluate the performance of an online processing system, which describes response time?
  8. In a system, each user request is processed in order by a web server tier, an application server tier and a database server tier. Each request passes through each of the three tiers once, and the maximum number of requests each tier can process is 1,200 per second for the web server tier, 1,000 per second for the application server tier and 900 per second for the database server tier. If the database server tier is upgraded to process 1,500 per second, which is the maximum number of requests the whole system can process?
  9. Which describes a dual system?
  10. 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?
  11. 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)?
  12. 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)?
  13. 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?
  14. Which is an example of a design based on the fail-soft concept?
  15. In semiconductor manufacturing equipment, normally closed gas supply valves that open with air pressure are used, so that if a power outage or a loss of compressed air occurs, the valves close and the supply of hazardous gas stops. Which design concept is this?
  16. Which is an example of a design based on the fool-proof concept?
  17. Among the approaches to improving system reliability, which corresponds to fault avoidance?
  18. Which describes RAID 1?
  19. RAID 5 is built from four disks with a capacity of 4 TB each. Which is the capacity available for storing data?
  20. RAID 6 is built from six disks with a capacity of 8 TB each. Which is the correct combination of the capacity available for storing data and the number of disks that can fail at the same time without losing data?
  21. In a RAID 10 array of four disks (two mirrored pairs, striped across the two pairs), two of the four disks fail at the same time. If every pair of disks is equally likely to be the one that fails, which is the probability that data is lost?
  22. RAID 5 is built from four disks, each capable of 200 random input/output operations per second (IOPS). Each small random write requires four I/O operations in total: reading the old data and the old parity, and writing the new data and the new parity; cache effects are ignored. When only writes are performed, which is the number of writes the whole RAID 5 array can process?
  23. Which describes a differential backup?
  24. A full backup is taken every Sunday night, and an incremental backup is taken every night from Monday to Saturday. A failure occurs at midday on Thursday, and it is decided to restore the data to the point of Wednesday night's backup. Which is the number of backups used for the restore?
  25. In a system with 500 GB of data in total, a full backup is taken every Sunday, and a differential backup is taken every night from Monday to Saturday. Each day, 20 GB of other data that had not been changed until then is changed. Which is the total size of the six differential backups from Monday to Saturday?
  26. In business continuity planning, which describes the RPO (recovery point objective)?
  27. For a system, the RPO (recovery point objective) is set at 4 hours and the RTO (recovery time objective) at 2 hours. A failure can occur at any time, and the time taken to make a backup is negligible. Which data protection scheme meets these targets?
  28. Database updates are replicated synchronously between two data centers 1,000 km apart. For each update, the system waits for one round trip: the transfer to the other site and the notification that the write is complete. Taking the speed of light in optical fiber as about 200,000 km/s and the fiber route length as equal to the straight-line distance, which is closest to the increase in the response time of one update caused by propagation alone?
  29. In an IaaS cloud service, which does the user generally manage?
  30. Among the ways to increase a system's processing capacity, which corresponds to scale-out?
  31. Which is generally a desirable design for a system that uses autoscaling to add and remove servers automatically according to the load?
  32. Which describes live migration in a virtualized environment?
  33. Which describes a CDN (content delivery network)?
  34. In a semiconductor fab, the aim is to detect abnormalities quickly using sensor data collected at high frequency from many pieces of manufacturing equipment. Instead of sending all the data to a distant cloud for processing, edge computing processes it on computers placed near the equipment. Which is a main advantage of using edge computing?
  35. Among the ways of connecting storage, which describes a SAN (storage area network)?
  36. From a storage pool with a physical capacity of 100 TB, 30 volumes with a logical capacity of 5 TB each were created using thin provisioning. Currently, on average 40% of each volume's logical capacity has been written, and the data grows by a total of 2 TB each week. Ignoring data deletion and compression, when will the pool's utilization reach 80%?
  37. A data center has IT equipment consuming 800 kW, cooling facilities consuming 280 kW, and power facility losses, lighting and so on amounting to 120 kW. When the cooling method is improved so that only the power consumption of the cooling facilities is halved, which is the PUE?
  38. Which is the reason for combining a UPS (uninterruptible power supply) with on-site generators in a data center?
  39. Which describes the hot aisle/cold aisle concept used in arranging server racks in a data center?
  40. A web system that must process 1,800 requests per second at peak is being designed. One server can process at most 250 requests per second, and each server's utilization should be kept at 70% or less. In addition, the remaining servers must still meet this condition if one server fails (N+1 configuration). With the load spread evenly, which is the minimum number of servers required?

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