Hybrid Non-Volatile Cache Memory for Power Loss Data Backup
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Solution Overview
Problem
Data storage devices, particularly those using shingled magnetic recording (SMR) technology, face issues with data loss and corruption due to sudden power loss, leading to operating system errors and performance issues, as they struggle to save sufficient information during power disruptions.
Innovation Solution
A data storage device configuration that includes a non-volatile cache memory system with a master device and two slave devices, one using NOR Flash and the other using Ferroelectric Random-Access Memory (FeRAM), allowing for frequent data logging and backup during power loss, with FeRAM providing faster write capabilities and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NOR Flash is used as non-volatile cache memory in smaller drives, then data backup capability is provided, but programming overhead increases and write speed decreases
Solution Approach 1:
The non-volatile cache memory is segmented into two distinct memory types: NOR Flash for data backup and FeRAM for frequent logging. This segmentation allows each memory type to be optimized for its specific function, with FeRAM handling high-speed write operations and NOR Flash providing reliable backup storage, thereby resolving the contradiction between backup capability and write speed.
Solution Approach 2:
FeRAM acts as an intermediary between the volatile cache and NOR Flash. During normal operation, data is logged to FeRAM which provides fast write capability. Upon power loss, the controller captures data from FeRAM and transfers it to NOR Flash for permanent backup. This intermediary approach eliminates the programming overhead of NOR Flash for frequent writes while maintaining backup capability.
2Reliability
If NOR Flash is used for frequent data logging, then data retention during power loss is improved, but programming overhead and power consumption increase
Solution Approach 1:
The system segments the logging function from the backup function. FeRAM is used for frequent logging operations during normal operation, consuming minimal power. NOR Flash is used only for backup operations triggered by power loss events. This segmentation reduces overall power consumption while maintaining data retention capability.
Solution Approach 2:
Instead of continuously writing to NOR Flash, the system uses FeRAM for continuous logging and only periodically transfers data to NOR Flash upon power loss detection. This periodic action approach minimizes power consumption associated with NOR Flash programming operations while ensuring data is preserved during power disruptions.
3Device complexity
If only single-type non-volatile cache memory is used, then device complexity is reduced, but ability to save sufficient information during power loss is limited
Solution Approach 1:
The patent applies the composite materials principle by combining two different non-volatile memory types (NOR Flash and FeRAM) in a hybrid memory system. Each memory type contributes its unique strengths: NOR Flash provides high reliability for backup and FeRAM provides fast write capability for frequent logging. This composite approach enables the system to save sufficient information during power loss without excessive complexity.
Data Source
AI summary
A data storage device includes a main storage memory and a non-volatile cache memory system. The non-volatile cache memory system comprises a master device, a first slave device communicatively coupled to the master device, the first slave device comprising a first non-volatile memory, and a second slave device communicatively coupled to the master device, the second slave device comprising a second non-volatile memory of a different type than the first non-volatile memory. The data storage device also includes a controller communicatively coupled to the main storage memory and to the non-volatile cache memory system, the controller is configured to, upon a power loss to the data storage device, store volatile data into the non-volatile cache memory system.