SSD Erase Block Type Detection for UGSD Recovery
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Solution Overview
Problem
Current storage device controllers in SSDs face inefficiencies due to the inability to identify the erase block type during ungraceful shutdowns (UGSD), leading to unnecessary program-erase cycle (PEC) increments, which impact the lifespan and reliability of SSDs, particularly in high-scalable NAND technologies like QLC and PLC.
Innovation Solution
Implement an erase type detection mechanism in the controller to identify the erase block type after UGSD by performing page0read and direct memory count (DMC) operations, allowing the controller to avoid unnecessary flash fill and erase operations, ensuring the same block type is used for subsequent programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller performs an additional erase operation to synchronize block type information after unexpected power reset, then the block type information is synchronized for the next program operation, but the Program-Erase Cycle (PEC) count of the block increases unnecessarily, negatively impacting the SSD's lifespan
Solution Approach 1:
The controller performs a read operation on the erased block before the power loss event to identify and store the erase block type information. This preliminary identification allows the controller to retrieve the stored block type information after power restoration, avoiding the need for additional erase operations to synchronize block type information and thereby preventing unnecessary PEC count increases
Solution Approach 2:
The controller creates a copy of the erase block type information by reading the block status before power loss and storing it in memory. This copied information can be retrieved after power restoration without requiring physical re-erasure of the block, thus preserving the PEC count while maintaining accurate block type synchronization
2Duration of action of stationary object
If the controller performs read operations to identify erase block type after power loss, then unnecessary erase operations are avoided, but additional read operations are required following power loss event
Solution Approach 1:
The controller performs the block type identification read operation before the power loss event occurs, storing the results in memory. After power restoration, the controller can directly use the pre-stored block type information without needing to perform additional read operations, thereby eliminating the time loss while still achieving the goal of avoiding unnecessary erase operations
Data Source
AI summary
Aspects of a storage device are provided for handling detection and operations associated with an erase block type of the block. The storage device includes one or more non-volatile memories each including a block, and one or more controllers operable to cause the storage device to perform erase type detection and associated operations for single blocks or metablocks. For instance, the controller(s) may erase the block prior to a power loss event, perform at least one read of the block following the power loss event, identify the erase block type of the block in response to the at least one read, and program the block based on the identified erase block type without performing a subsequent erase prior to the program. The controller(s) may also perform metablock operations associated with the identified erase block type. Thus, unnecessary erase operations during recovery from an ungraceful shutdown (UGSD) may be mitigated.