SSD Controller Dual RAM Data Integrity Protection
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Solution Overview
Problem
Storage devices, such as SSDs, face challenges in data reliability due to limited RAM capacity, which is consumed by parity data and data in flight, leading to potential data loss during power failures.
Innovation Solution
The implementation of a storage device with a controller that utilizes two volatile memory units (RAM1 and RAM2) to generate and store change log data, updating delta data, and periodically copying it to a non-volatile storage unit, ensuring data integrity during power failures by copying delta and change log data to the storage unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parity data is generated and stored in RAM for each write command, then data reliability is improved, but RAM space is consumed and device cost increases
Solution Approach 1:
The patent segments parity data into two categories: critical parity data that must be protected and non-critical parity data that can be lost. By applying different protection strategies to different segments, the system achieves reliable data protection while minimizing RAM consumption. Critical user data receives full parity protection, while parity data itself is treated as non-critical and allowed to be lost without compromising overall data integrity.
Solution Approach 2:
The patent extracts parity data from the critical protection category and treats it separately from user data. By taking out parity data from the set of data requiring protection, the system avoids generating redundant parity for parity itself, thereby reducing RAM space requirements while maintaining data reliability for actual user information.
2Productivity
If data in flight is stored in RAM, then write performance is improved, but RAM space is consumed and data loss risk increases during power failure
Solution Approach 1:
The patent converts the harmful effect of potential data loss into a beneficial selective loss strategy. By determining that parity data can be safely lost without compromising data integrity, the system allows parity data in flight to be discarded during power failures. This transforms the potential harm into a benefit by simplifying the power failure response while maintaining data reliability through selective protection of only critical user data.
3Reliability
If dedicated die or plane is allocated for parity data in each stream, then data protection is improved, but storage capacity is reduced
Solution Approach 1:
The patent applies partial protection action by protecting only the necessary portion of data (critical user data) rather than protecting all data including parity data. This partial approach achieves sufficient data protection for actual user information while avoiding the excessive allocation of dedicated storage resources, thereby maximizing usable storage capacity.
Data Source
AI summary
The present disclosure generally relates to methods of operating storage devices. The storage device comprises a controller comprising first random access memory (RAM1), second random access memory (RAM2), and a storage unit divided into a plurality of streams. When a write command is received to write data to a stream, change log data is generated and stored in the RAM1, the previous delta data for the stream is copied from the RAM2 to the RAM1 to be updated with the change log data, and the updated delta data is copied to the RAM2. The delta data stored in the RAM2 is copied to the storage unit periodically. The controller tracks which delta data has been copied to the RAM2 and to the storage unit. During a power failure, the delta data and the change log data are copied from the RAM1 or the RAM2 to the storage unit.