Unmap Request Processing in Nonvolatile Memory Buffer
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Solution Overview
Problem
Current data storage devices face inefficiencies in processing unmap requests, which can consume significant resources and time due to the need for updating and matching physical-to-logical (P2L) and logical-to-physical (L2P) maps, especially when handling unmap requests from host devices.
Innovation Solution
A data storage device with a nonvolatile memory device and a buffer memory block that temporarily stores data, using a control unit to store unmap addresses and flag information in an empty page of the buffer memory block and update the P2L map, allowing for efficient processing of unmap requests by prioritizing P2L map updates and deferring L2P map updates to minimize resource consumption and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data storage device updates both P2L map and L2P map when processing unmap requests, then the address mapping information is kept synchronized, but the processing time and resource consumption increase significantly
Solution Approach 1:
The patent divides the map update process into two separate segments: P2L map updates are performed immediately when unmap requests are received, while L2P map updates are deferred and performed in batches during garbage collection operations. This segmentation allows the system to maintain address mapping consistency without the performance penalty of synchronous dual-map updates.
Solution Approach 2:
The patent performs preliminary updates to the P2L map when unmap requests are received, marking the affected physical blocks as invalid. The corresponding L2P map updates are then performed preliminarily during garbage collection, rather than immediately, reducing the time critical path for unmap request processing.
2Measurement precision
If the data storage device processes unmap requests by updating all address maps immediately, then the mapping accuracy is maintained, but the device complexity and resource consumption increase
Solution Approach 1:
The patent implements a dynamic update strategy where the timing of L2P map updates is flexible and depends on the garbage collection schedule rather than being rigidly synchronized with every unmap request. This dynamic approach reduces control complexity while maintaining mapping accuracy through periodic synchronization.
Solution Approach 2:
The garbage collection process serves dual purposes: it manages memory block lifecycle and simultaneously updates the L2P map with unmap information. This self-service approach eliminates the need for a separate dedicated update mechanism, reducing overall system complexity.
3Measurement precision
If the data storage device updates the L2P map for every unmap request, then the logical-to-physical mapping remains accurate, but the productivity and throughput decrease
Solution Approach 1:
The patent implements periodic batch updates of the L2P map during garbage collection cycles, rather than continuous individual updates for each unmap request. This periodic action maintains mapping accuracy while significantly improving throughput by reducing the frequency of write amplification operations.
Solution Approach 2:
The patent discards the immediate update approach for L2P maps and recovers the update operation by performing it asynchronously during garbage collection. This allows unmap requests to be processed quickly while still maintaining mapping accuracy through subsequent batch updates.
Data Source
AI summary
A method for operating a data storage device which uses a nonvolatile memory device including a buffer memory block which temporarily stores data, as a storage medium, includes receiving an unmap request which requests that an unmap address be erased, from a host device; storing the unmap address and flag information indicating that the unmap address is unmapped, in a first empty page of the buffer memory block; and mapping the unmap address and flagging flag information indicating that the unmap address is unmapped, in a physical-to-logical (P2L) map corresponding to the first empty page of the buffer memory block.