SSD Garbage Collection Handling Uncorrectable Read Errors
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Solution Overview
Problem
In SSDs, uncorrectable read errors can prevent garbage collection, leading to exhaustion of the GC destination logical block and inefficient use of storage space due to the coexistence of valid and invalid clusters within physical blocks.
Innovation Solution
A storage device and method that designates a GC original logical block even with uncorrectable read errors, performs garbage collection by reading data from physical blocks, creating a new logical block, and updating tables to associate physical blocks with the new logical block, thereby allowing garbage collection to proceed and preventing GC destination logical block exhaustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If garbage collection is performed by reading data from physical blocks, then storage space can be effectively reused, but uncorrectable read errors prevent the garbage collection process from completing
Solution Approach 1:
The system performs preliminary actions by creating a new logical block and updating the mapping table before attempting to read data from physical blocks. This preliminary setup allows the system to continue garbage collection even when read errors occur, as the new logical block can serve as an alternative destination for valid data.
Solution Approach 2:
The patent introduces a new logical block as an intermediary between the GC original logical block and the storage system. This intermediary allows the garbage collection process to proceed by providing an alternative path for data migration when read errors occur in the original logical block.
2Quantity of substance
If the size of the physical block increases, then storage capacity increases, but storage area cannot be utilized effectively due to coexistence of valid and invalid clusters
Solution Approach 1:
The patent segments the logical block structure by creating a new logical block separate from the GC original logical block. This segmentation allows independent management of data migration and enables effective utilization of storage space by clearly distinguishing between valid and invalid clusters across different logical blocks.
3Ease of operation
If a read error occurs and cannot be corrected, then the cluster validity cannot be determined, but the patent allows designating a new logical block to continue garbage collection
Solution Approach 1:
The patent changes the parameter of logical block association by updating the mapping table to associate physical blocks with a new logical block instead of the original one. This parameter change enables the system to continue garbage collection operations despite read errors, maintaining operational continuity.
Data Source
AI summary
A storage device includes a nonvolatile memory with physical blocks each including a plurality of clusters, and a controller that maintains a first table storing a relationship between a logical address and a physical address of the cluster, and a second table storing a relationship between a logical block and physical blocks allocated thereto. The controller performs garbage collection processing which includes copying data read from valid clusters of the first logical block to a destination logical block, creating a new logical block when the data read contains an uncorrectable error, allocating the physical blocks of the first logical block to the new logical block, and updating the second table so that the physical blocks of the first logical block are associated with the new logical block and no physical blocks are associated with the first logical block.