Replication techniques in the context of fault tolerance
1. Full Replication
Complete duplication of system or data across multiple nodes.
Implementation: Every node maintains an identical copy of the entire system or dataset.
Advantages of Full Replication:
- Straightforward fault tolerance.
- Seamless switch to a backup node in case of failure.
Challenges of Fulll Replication:
- Resource-intensive, as each node hosts a full replica.
- Synchronization mechanisms are crucial for consistency.
2. Partial Replication
Selective duplication of critical components or data.
Implementation: Replicates only essential elements for system functionality, optimizing resource usage.
Advantages of Partial Replication:
- Resource efficiency.
- Focuses on replicating key components.
- Requires careful selection of components for replication.
Challenges of Partial Replication:
- Complexity in determining which parts are critical.
- Synchronization challenges for selectively replicated components.
3. Shadowing or Passive Replication
Maintaining passive copies that activate only upon primary system failure.
Implementation: Inactive replicas become active when the primary system encounters a fault.
Advantages of Shadowing or Passive Replication:
- Resource efficiency during normal operation.
- Quick response in case of a failure.
Challenges of Shadowing or Passive Replication:
- Synchronization during the transition from passive to active state.
- Effective fault detection mechanisms are crucial.
4. Active Replication:
All replicas actively process the same inputs concurrently.
Implementation:
Requests are distributed to all replicas, and their outputs are compared to determine the correct result.
Advantages of Active Replication:
- High fault tolerance.
- Continued processing even if some replicas fail.
Challenges of Active Replication:
- Increased communication overhead due to multiple replicas actively processing.
- Managing consistency among active replicas is complex.
Fault Tolerance in System Design
Fault tolerance is the ability of a system to continue performing, or at least minimize downtime, even when some components fail.
Important Topics for Fault Tolerance in System Design
- What is Fault Tolerance?
- Different situations where fault tolerance is crucial
- Replication techniques in the context of fault tolerance
- Fault Tolerance vs. High Availability Load Balancing
- Fault Tolerance of a Stateless Component
- Fault Tolerance of a Stateful Webstore
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