Comparing Persistence: Redis vs NCache
Data persistence is crucial in distributed caching as it ensures high availability, disaster recovery, and durability. Both Redis and NCache offer persistence features, but their approaches differ significantly. Let's discuss why persistence is essential, compare Redis and NCache in terms of persistence mechanisms, and highlight why NCache provides a more reliable solution for modern applications.
Why Persistence Matters in a Distributed Cache
Caching is typically volatile, but persistence solves this issue by ensuring that cached data remains available even after system failures, restarts, or crashes. Persistence is particularly valuable in scenarios where:
- Applications experience unexpected crashes or reboots.
- Infrastructure failures like power outages or cloud disruptions occur.
- Costly database operations need to be reduced by maintaining cached data.
- Quick cache recovery is needed for scalability and disaster recovery.
By incorporating persistence, distributed caches can minimize data loss risks and enhance recovery times to ensure consistent performance and availability.
Overview of Redis Persistence
Redis provides multiple persistence mechanisms, each with its own advantages and trade-offs.
Redis Persistence Options
- RDB (Redis Database): It takes periodic snapshots of data at defined intervals, which offers durability but with a risk of data loss if the server crashes between snapshots.
- AOF (Append-Only File): Logs every write operation that allows full data recovery at the cost of increased storage consumption.
- Hybrid Mode (AOF + RDB): A combination of both methods that balances durability while optimizing storage usage.
Limitations of Redis Persistence
- Data Loss in RDB due to Long Backup Intervals: Any data changes between snapshots are lost if the server crashes before the next scheduled backup because RDB takes snapshots periodically. This increases the risk of inconsistency, especially in high-transaction environments.
- High Memory Consumption with AOF: AOF logs every write operation, which can significantly increase storage requirements, making it inefficient for write-heavy applications.
- No Automatic Recovery from RDB and AOF: Manual intervention is required to restore data from RDB and AOF, leading to increased downtime. This process of restoring data manually can be time-consuming, especially for large datasets.
- Limited Integration with Redis Clustering: Persistence in Redis is not fully integrated with its clustering feature which leads to operational complexities when scaling.
Why Choose NCache Live Persistence?
NCache offers an advanced live persistence mechanism that is designed for high performance, seamless scalability, and real-time durability.
Live Persistent Data Store
NCache ensures real-time data consistency and high availability by maintaining a live persistent data store that is updated in near real-time with a 1-second delay by default. Every cache update is automatically applied to the persistent store, reducing the risk of data loss and ensuring reliability.
Performance:
- Client Cache (InProc Speed): Client Cache sits directly on the application server and can even function as an in-process cache to speed up data retrieval, which reduces round trips to the distributed cache.
- Asynchronous Persistence: It ensures that writes to the persistence store function in the background without affecting application performance.
Linear Scalability:
- Bucket Level Persistence: The entire cache is divided into 100 buckets, ensuring that all persistence operations occur at the bucket level. This structure optimizes data distribution, improves storage utilization and enables seamless node additions/removals without disrupting caching operations.
- Add/Remove Nodes at Runtime: When nodes are added or removed at runtime, data gets automatically loaded from the persistent store, which allows continuous availability and smooth scaling while maintaining persistence across all data buckets.
High Availability and Fault Tolerance
NCache ensures data availability even in failure scenarios.
- Data Persistence with Node Changes: It maintains data integrity and availability even when nodes are added or removed.
- Data Recovery on Restart: Cached data is instantly restored upon service restart.
- Automatic Data Rebalancing: Data is evenly redistributed when nodes join or leave.
NCache Advanced Persistence Store
NCache's persistence store is designed for efficiency and minimal performance overhead.
Near Real-Time Persistence
- Live Persistent Data Store: NCache maintains a live persistent data store that updates in near real-time with a default 1-second delay. This ensures minimal data loss and quick recovery in case of failures.
Centralized Persistent Store
- Persistence at the bucket level: The entire cache is represented by 100 buckets, and all persistence operations occur at the bucket level. This approach maximizes efficiency and balanced resource usage.
Asynchronous Persistence Mechanism
- Async Queue is Replicated: In case of Partition-Replica Cache, the queue is replicated on the Replica node to ensure high availability and prevent data loss in case of primary node failure.
- Non-Blocking Writes: All write operations are enqueued and processed asynchronously, which ensures minimal disruption to cache performance.
Configurable Quick Persistence Interval
- Default persistence interval to 1 second: This ensures near real-time durability by committing changes to the persistent store frequently. The short interval minimizes data loss and allows for quick recovery in case of failures.
Automatic Data Loading from Persistent Store
NCache automatically loads data from the persistent store and treats it like a database that has a copy of its data in-memory as well. The database gets updated every time the in-memory copy is updated to maintain consistency and durability.
- Cache Startup: Data is automatically loaded from the persistent store to ensure availability.
- Node Join: When a node joins the cluster, it automatically retrieves relevant data from the persistent store.
- Node Leave: Data is automatically rebalanced across remaining nodes from the persistent store.
Powerful Persistence Monitoring
- Performance Tracking: NCache provides comprehensive performance counters to track persistence efficiency.
- Real-Time Monitoring: Dashboard-style NCache Monitor for real-time visibility into persistence operations.
How to Configure NCache Persistence?
Install NCache Server
- Download and install NCache on your caching nodes.
Configure NCache Persistence
- Enable persistence in the NCache Management Center.
- Specify the persistence store location (SQL, cloud storage, etc.).
- Define backup intervals and monitoring settings to optimize performance.
Conclusion
Persistence in distributed caching is critical for data reliability, availability, and disaster recovery. While Redis offers multiple persistence options, NCache stands out with its advanced persistence features which includes:
- Near real-time persistence that is faster and memory-efficient than Redis.
- Asynchronous writes that ensure minimal impact on performance.
- High availability, dynamic scalability, and automatic data rebalancing.
- Robust monitoring tools for real-time performance insights.
For enterprises looking for a highly available, scalable, and performance-optimized persistence store, NCache is the ideal choice. Try NCache today for a seamless distributed caching experience!