Centralized vs Distributed vs Decentralized System

Centralized system

Definition of centralized system

System that use client/server architecture, where one or more clients node are connected to a central server.

Advantages of centralized system

• Easy to physically secure;

• Quick updates (only one server to update);

• Easy to manage: owner has just to manage one server, no need to manage clients;

• Full control of the system by the owner.

Disadvantages of centralized system

• Single point of failure: if the server is down, the system is down;

• Centralized control (disadvantage for users);

• Difficult server maintenance (only hot updates are possible, may break the system);

• Less possibility of data backup (redundancy must be applied);

• Difficult to scale (server must be upgraded to handle more clients);

• DDOS attack (server can be overloaded by malicious users).

Applications of centralized system

• Application development (especially for web applications);

• Data analysis: easier analysis when data is centralized;

• Data storage;

• Personal computing.

Distributed system

Definition of distributed system

System that uses peer-to-peer architecture, where nodes interact with each other to achieve a common goal.

Advantages of distributed system

• Low latency: because of high geographical nodes distribution, time to get a response is low;

• High scalability: nodes can be added to the system to handle more clients or more computing power.

Disadvantages of distributed system

• Still under the control of the owner.

Applications of distributed system

• Cluster computing: computers are coupled together to work as a single system, to achieve a common goal;

• Grid computing: All the resources are pooled together in order to turn the system into a single supercomputer;

• Cloud computing.

Decentralized system

Definition of decentralized system

System that uses peer-to-peer architecture, where each node operates on its own on local data to accomplish global goals.

Advantages of decentralized system

• Minimal bottleneck: the entire load is balanced across all nodes;

• No single point of failure (high availability): if one node is down, the system is still up;

• No central authority / Trustless: no one can control the system;

• Easy to scale: nodes can be added so it increases the performance of the entire system and lead to a more decentralized system;

• Redundancy: data is always replicated on all nodes.

Disadvantages of decentralized system

• Hard to sync: a consensus algorithm must be used to sync all nodes;

• No central authority: since nodes themselves are in charge of the security, if 51% of the nodes are malicious, the system is compromised;

• Complexity: difficult to understand, deploy, maintain & debug.

Applications of decentralized system

• Blockchain;

• Data storage;

• Data base.

Comparison

	Centralized	Distributed	Decentralized
Network/hardware resources	Maintained & controlled by single entity in a centralized location	Spread across multiple data centers & geographies; owned by network provider	Resources are owned & shared by network members; difficult to maintain since no one owns it
Solution components	Maintained & controlled by central entity	Maintained & controlled by solution provider	Each member has exact copy of distributed ledger
Data	Maintained & controlled by central entity	Typically owned & managed by customer	Only added through group consensus
Control	Controlled by central entity	Typically, a shared responsibility between network provider, solution provider & customer	No one owns the data & everyone owns the data
Single point of failure	Yes	No	No
Fault tolerance	Low	High	Extremely high
Security	Maintained & controlled by central entity	Typically, a shared responsibility between network provider, solution provider & customer	Increases as number of nodes increases
Performance	Maintained & controlled by central entity	Increases as network/hardware resources scale up and out	Decreases as number of nodes increases
Example	ERP system	Cloud computing	Blockchain