Fast Response Cache With Intelligent Copyback For SSD Data Transfer
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Solution Overview
Problem
Current data storage devices, such as solid-state drives (SSDs), face challenges in enhancing data transfer performance and reliability due to limitations in cache management strategies, particularly in efficiently transferring data between a cache and main memory while maintaining error correction and minimizing latency.
Innovation Solution
The implementation of a dedicated fast response cache (FRC) with programmable controllers that apply different error correction encoding schemes (ECC1 and ECC2) to data, allowing for direct or indirect transfer from the FRC to the main memory, optimizing data paths through parallel channels and utilizing specially configured flash memory cells for reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data is transferred directly from cache to main memory, then transfer speed is improved, but data integrity and error correction reliability deteriorate
Solution Approach 1:
A dedicated error correction circuit is introduced as an intermediary component between the cache and main memory. This circuit applies error correction encoding (such as LDPC or BCH codes) to data during the transfer process, ensuring data integrity while maintaining direct transfer paths for high speed. The error correction circuit processes data in real-time without requiring cache copyback operations.
2Reliability
If traditional cache copyback strategy is used, then data is transferred through established paths, but transfer latency increases and I/O performance deteriorates
Solution Approach 1:
The error correction function is extracted from the traditional cache copyback path and implemented as a separate dedicated circuit. This allows data to bypass the cache copyback mechanism entirely and be transferred directly to main memory while error correction is applied independently, eliminating the latency associated with cache management operations.
Solution Approach 2:
Error correction encoding is applied preliminarily to data before it leaves the cache, rather than waiting for cache copyback operations. This preliminary error correction ensures that data is protected against errors during transfer, and the main memory receives ready-to-store corrected data without additional processing delays.
3Reliability
If error correction is applied to all data transfers, then data integrity is improved, but processing overhead and complexity increase
Solution Approach 1:
Error correction is applied locally at the cache output interface rather than throughout the entire data path. The dedicated error correction circuit processes only the data leaving the cache, applying appropriate error correction codes (such as LDPC for high reliability requirements or BCH for lower overhead) based on the specific data characteristics and system requirements, rather than uniformly processing all data transfers.
4Ease of operation
If cache management is simplified, then device operation is easier, but data transfer performance and reliability deteriorate
Solution Approach 1:
The error correction circuit operates autonomously without requiring complex cache management interventions. Data flows directly from cache to main memory through the self-service error correction circuit, which automatically encodes and corrects errors without needing controller involvement or cache state management, thereby maintaining operational simplicity while ensuring data integrity.
Data Source
AI summary
Method and apparatus for intelligent caching, protection and transfers of data between a cache and a main memory in a data storage environment, such as but not limited to a solid-state drive (SSD). A main memory (MM) has non-volatile memory (NVM) cells configured for persistent storage of user data. A fast response cache (FRC) has NVM cells configured to provide storage of first data prior to transfer to the MM. A write cache (WC) has NVM cells configured to provide storage of second data prior to transfer to the MM. A controller directs input data to either the FRC or the WC. A first type of error correction encoding (ECC1) is applied to the first data and a different, second type of error correction encoding (ECC2) is applied to the second data. Data may be sent from the FRC to the MM either directly or through the WC.