Unmap Component for Coarse Mapping Memory Sub-system
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Solution Overview
Problem
Coarse mapping memory sub-systems lack inherent structures for efficient unmap operations, leading to performance delays due to the need for overwriting unmapped data, which can take several minutes and results in end-to-end CRC errors, consuming additional host resources and increasing latency.
Innovation Solution
The implementation of a unmap component within the memory sub-system that allows immediate serving of trim or unmap commands, tracks data to prevent CRC errors, and manages read and write operations by scheduling overwrite operations in the background, reducing latency and resource consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overwrite operations are performed to prevent CRC errors in coarse mapping memory sub-systems, then data integrity is improved, but operation latency increases significantly
Solution Approach 1:
The patent applies preliminary action by performing overwrite operations in advance before trim commands are executed. The system proactively overwrites data in memory blocks that are likely to be trimmed soon, so when a trim command arrives, the data is already overwritten and no additional latency is incurred. This resolves the contradiction by preparing the system ahead of time to maintain data integrity without delaying subsequent operations.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining a cushion of already-overwritten data blocks ready for immediate trim operations. The system anticipates trim requests and pre-overwrites data, creating a buffer that cushions against the latency that would otherwise occur when trim commands are received. This ensures data integrity is maintained while minimizing the time impact on operations.
2Reliability
If overwrite operations are performed immediately upon trim commands, then CRC errors are prevented, but host resource consumption increases
Solution Approach 1:
The patent applies self-service by implementing a background thread that autonomously manages overwrite operations without requiring active host intervention. The background thread continuously monitors memory blocks and performs overwrites automatically when conditions are appropriate, freeing the host from the energy-intensive task of managing each overwrite operation individually. This maintains CRC error prevention while reducing host resource consumption.
Solution Approach 2:
The patent implements continuity of useful action by having the background thread continuously perform overwrite operations in the background without interrupting host operations. The useful action of preventing CRC errors continues uninterrupted through the background thread's persistent monitoring and overwriting, while the host can proceed with other tasks without energy-intensive interruptions.
3Reliability
If coarse mapping memory sub-systems perform unmap operations by overwriting data, then data security is improved, but productivity decreases due to time-consuming operations
Solution Approach 1:
The patent applies preliminary action by pre-overwriting data in memory blocks before trim commands are issued. This proactive approach ensures that when unmap operations are needed for data security, the data is already overwritten, eliminating the need for time-consuming overwrite operations at the moment of trimming. This maintains data security while dramatically improving unmap operation speed.
Solution Approach 2:
The patent implements beforehand cushioning by creating a cushion of pre-overwritten data blocks that are ready for immediate secure deletion. The background thread continuously prepares data blocks by overwriting them in advance, creating a buffer of secure blocks that can be quickly allocated for trim operations. This ensures data security is maintained while productivity increases because the actual unmap operations become nearly instantaneous.
Data Source
AI summary
Devices, methods, and media are described for unmap support in coarse mapped storage. In one embodiment a controller of a memory sub-system manages a set of metadata for super management units (SMU) of the memory sub-system, wherein each SMU of the memory sub-system comprises a plurality of data management units (MU), and wherein each MU comprises a plurality of addressable memory elements as part of a coarse memory storage of the memory sub-system. The controller processes a trim command for a first SMU of the plurality of SMUs, and adjusts a trim bit associated with metadata for the first SMU. This trim bit can then be used to manage read and write operations as the trimmed unit waits to be written with an unmap data pattern. Similarly, a trim bit in MU metadata can be used manage related operations to prevent memory access errors.