--- title: "Centralized vs distributed; design issues" subject: "Distributed System" chapter: 1 key: "semester_7/distributed_system:centralized-vs-distributed" source: https://www.bctengineer.com/q/semester_7/distributed_system/centralized-vs-distributed site: BCT Engineering --- # Centralized vs distributed; design issues Distributed System · Chapter 1: Introduction - Asked in: 2072 Chaitra, 2+6 marks - Video: [Centralised Systems vs. Distributed Systems](https://www.youtube.com/watch?v=GREM05ZRK4g) — kodebot - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/distributed_system/centralized-vs-distributed - Whole chapter: https://www.bctengineer.com/md/semester_7/distributed_system/chapter-1 ## Question Differentiate between centralized and distributed system. Explain the design issues related to distributed system. ## Short answer Centralized system has one central computer with single control and single point of failure; distributed system has independent networked nodes with partial failures and better scalability. Design issues include transparency, communication, naming, process and resource management, consistency and replication, synchronization, fault tolerance, scalability, security, and heterogeneity. ## Answer #### Centralized versus distributed system | Point | Centralized system | Distributed system | |---|---|---| | Nodes | One central computer, users use terminals | Many independent computers on a network | | Control | Single point of control | Control and data are spread over nodes | | Failure | Single point of failure; whole system stops | Partial failure; remaining nodes continue | | Scalability | Limited by the central machine | Grows by adding nodes | | Cost | Costly mainframe | Cheaper commodity machines | | Resource sharing | Local only | Across the network | | Response time | Falls when the load grows | Better through load sharing | | Clock and memory | Shared memory and one clock | No shared memory, no global clock | | Security and management | Easier | Harder | | Example | Mainframe with terminals | Web, cloud | #### Design issues 1. **Transparency:** what to hide (access, location, replication, failure...) and at what cost. 2. **Communication:** choice of message passing, RPC, RMI, group communication and protocols. 3. **Naming:** unique, location independent names and an efficient name service (DNS). 4. **Process and resource management:** scheduling, load balancing, thread use, migration. 5. **Consistency and replication:** keep copies consistent while providing speed. 6. **Synchronisation and time:** no global clock; need logical clocks, mutual exclusion and election. 7. **Fault tolerance:** detection, masking and recovery. 8. **Scalability and performance:** avoid bottlenecks, use caching. 9. **Security:** authentication, authorisation and secure channels. 10. **Heterogeneity and openness:** standard interfaces, middleware. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does failure differ between centralized and distributed systems? A. Centralized has a single point of failure; distributed has partial failure while others continue B. Distributed stops completely on one failure C. Both have no failures D. Centralized continues when its central machine fails Answer: A. A centralized system stops entirely if the central machine fails; a distributed system degrades partially. (Key point: Failure comparison) 2. Which is true for a distributed system's clock and memory? A. Shared memory and one global clock B. No shared memory and no global clock C. One shared memory only D. One global clock only Answer: B. Centralized systems have shared memory and one clock; distributed ones do not. (Key point: Clock and memory) 3. Why are logical clocks, mutual exclusion and election needed? A. Because every node has the same clock B. Because there are no processes C. Because there is no global clock, so synchronisation must be done by algorithms D. Because naming is trivial Answer: C. Synchronisation and time is a design issue arising from absence of a global clock. (Key point: Design issue: synchronisation) 4. What should a good naming scheme in a distributed system provide? A. Names that encode the server's physical place B. Names that change each time they are used C. No names at all D. Unique, location independent names with an efficient name service such as DNS Answer: D. Naming must be unique and location independent, supported by a name service. (Key point: Naming) ## Related in Distributed System - [Autonomous vs distributed system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Aautonomous-vs-distributed) — Distributed System, chapter 1 - [DS vs centralized; layers of transparency](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Ads-over-centralized-transparency) — Distributed System, chapter 1 - [Centralized vs Ricart-Agrawala algorithm](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Acentral-vs-ra-compare) — Distributed System, chapter 6 - [Network OS vs distributed OS](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Anos-vs-dos-diff) — Distributed System, chapter 3 - [Models of distributed system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Amodels-of-ds) — Distributed System, chapter 1 - [True distributed system; middleware organisation](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Atrue-ds-middleware) — Distributed System, chapter 3 ## Related in other subjects - [Short note: Distributed system implementation](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Ashort-note-distributed-implementation-issues) — Object Oriented Analysis and Design, chapter 4 - [Medium network design issues and proxy servers](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Adesign-medium-network-proxy) — Internet and Intranet, chapter 5 - [Lumped vs distributed analysis, applications, protocols](https://www.bctengineer.com/question.md?key=semester_7%2Frf_and_microwave_engineering%3Alumped-distributed-protocols) — RF and Microwave Engineering, chapter 1 - [Transmission line issues in high speed design](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Atransmission-line-issues) — Instrumentation II, chapter 7