Storage Device Flash Mapping Table Checkpointing
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Solution Overview
Problem
Existing storage systems face challenges in efficiently performing checkpointing operations, leading to prolonged checkpointing times, redundant data writing, and increased garbage collection frequencies due to the need to read and rewrite journal data across different logical and physical addresses.
Innovation Solution
The proposed solution involves a storage system that remaps a flash mapping table in response to checkpointing commands, allowing journal data to be reused and reducing the need for redundant writes by directly updating physical addresses, thereby offloading checkpointing operations from the host to the storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the storage device performs traditional checkpointing by reading and rewriting journal data across different logical and physical addresses, then checkpointing consistency is guaranteed, but checkpointing time is prolonged and redundant data writing increases
Solution Approach 1:
The patent applies preliminary action by pre-writing journal data to the physical address before the actual data write operation occurs. The flash mapping table is updated in advance to map the journal logical address to the target physical address, so that when checkpointing is needed, the data is already in its final position, eliminating the need for time-consuming read-rewrite operations during checkpointing.
Solution Approach 2:
The patent uses the flash mapping table as an intermediary structure that decouples the journaling process from the checkpointing process. By introducing this mapping layer, the system can track data locations without requiring actual data movement, and the journal logical address serves as an intermediary that points to the final physical location without requiring intermediate read-write operations.
2Reliability
If the storage device performs traditional checkpointing operations, then data consistency is safeguarded, but garbage collection frequency increases
Solution Approach 1:
The patent applies preliminary action by updating the flash mapping table in advance to reflect the final data location. This preliminary update eliminates the need for subsequent garbage collection operations that would otherwise be required to clean up old data references, as the mapping table directly points to valid data locations without creating obsolete references.
Solution Approach 2:
The patent applies discarding and recovering by allowing the journal logical address to be discarded after the data is successfully written to the target physical address and the mapping table is updated. The journal buffer space is then recovered and can be reused for new journaling operations, eliminating the need for garbage collection to reclaim this space.
3Loss of energy
If the storage device remaps the flash mapping table to perform checkpointing, then redundant writes are minimized, but mapping table complexity increases
Solution Approach 1:
The patent applies preliminary action by performing the mapping table update as part of the initial data write operation, before checkpointing is needed. This preliminary update ensures that the mapping table reflects the final data location, eliminating the need for subsequent remapping operations and reducing redundant writes without adding ongoing complexity.
Solution Approach 2:
The patent applies copying by creating a journal copy of the data in the journal buffer with a journal logical address that maps to the target physical address. This copy mechanism allows the system to track data locations without requiring complex remapping operations, as the journal logical address directly points to the final location through the pre-updated mapping table.
Data Source
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AI summary
A storage system includes a storage device having a nonvolatile memory with a first and a second physical address and a host configured to insert a first journal logical address and a first target logical address into a journal mapping table. The storage device includes a flash mapping table storing the first journal logical address mapped to the first physical address, and the first target logical address mapped to the second physical address; a circuit configured to write the first journal data to an area of the nonvolatile memory to the first physical address corresponding to the first journal logical address according to the first mapping state, based on the journaling command; and to change the first mapping state of the flash mapping table to a second mapping state in which the first target logical address is remapped to the first physical address, based on the checkpointing command.