SSD L2P Table Recovery via Periodic Backup
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Solution Overview
Problem
Solid state drives (SSDs) face issues with data loss and inaccurate rebuilding of logical-to-physical tables due to sudden power interruptions, especially when trim commands are issued before a power failure, leading to lost addresses and incomplete erasure of data.
Innovation Solution
The method involves performing backup actions for the logical-to-physical table contents at regular intervals, storing write data in blocks, and executing trim commands to change used blocks to unused blocks, with physical-to-logical data stored in a trim block, ensuring that the table can be accurately rebuilt during sudden power off and recovery by using backup and trim block data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the L2P table is stored in volatile memory for real-time updates, then the access speed and update efficiency are improved, but the data reliability deteriorates because the contents are lost when power is interrupted
Solution Approach 1:
The patent performs preliminary backup actions by periodically copying the L2P table contents from volatile memory to non-volatile memory before power interruption can occur. This ensures that even if power is lost, the most recent backed-up version of the L2P table can be recovered, resolving the contradiction between fast access (volatile memory) and data reliability (non-volatile storage).
Solution Approach 2:
The patent creates a copy of the L2P table contents and stores it in non-volatile memory. This copying mechanism allows the system to maintain the high-speed access characteristics of volatile memory while ensuring data persistence through the copied version in non-volatile memory, thus resolving the reliability issue without sacrificing access speed.
2Productivity
If trim commands are executed to change used blocks to unused blocks, then the storage space utilization is improved, but the information completeness deteriorates because the physical-to-logical data may be lost during sudden power off
Solution Approach 1:
The patent performs preliminary backup of physical-to-logical data to non-volatile memory before trim commands are executed. This ensures that even if power is interrupted during or after the trim operation, the physical-to-logical mapping information is preserved and can be recovered, resolving the contradiction between storage space optimization and information completeness.
Solution Approach 2:
The patent introduces non-volatile memory as an intermediary storage layer that temporarily holds physical-to-logical data during trim operations. This intermediary ensures that the mapping information is not lost even when blocks are marked as unused, allowing storage space to be reclaimed while preserving the necessary mapping data for future recovery.
3Device complexity
If the L2P table contents are not backed up to non-volatile memory, then the device complexity is reduced, but the loss of information increases during sudden power off events
Solution Approach 1:
The patent implements a relatively simple preliminary backup mechanism that periodically copies L2P table contents to non-volatile memory. This straightforward approach minimizes device complexity while effectively preventing data loss during sudden power off events, as the backup occurs automatically as part of normal operation without requiring complex error detection or recovery systems.
4Reliability
If backup actions are performed frequently to ensure data safety, then the reliability is improved, but the productivity deteriorates due to increased time consumption for backup operations
Solution Approach 1:
The patent implements periodic backup actions where the L2P table contents are copied to non-volatile memory at predetermined time intervals or after a certain number of write operations. This periodic approach balances reliability and productivity by ensuring data is backed up frequently enough to prevent loss during unexpected power failures, while avoiding excessive backup operations that would consume unnecessary time and reduce system throughput.
Data Source
AI summary
A data processing method for a solid state drive includes the following steps. When a write command is received, the write command is executed to store a write data into a first number of blocks of the plural blocks, a block-closing action is performed to generate a first number of used blocks, and the logical-to-physical table is updated. When a trim command is received, the trim command is executed to change a second number of used blocks to a second number of unused blocks, a physical-to-logical data corresponding to the second number of used blocks is stored into a trim block of the non-volatile memory, and the logical-to-physical table is updated. A backup action is performed at plural time points to generate plural backup contents corresponding to the plural time points, respectively. The plural backup contents are stored into the non-volatile memory.