SSD Copy-on-Write Snapshot via Logical Mapping
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Solution Overview
Problem
The conventional copy-on-write technique for creating snapshots on solid state drives (SSDs) is inefficient, requiring multiple read/write operations that consume significant memory and bandwidth, and reduces the effective life of SSDs due to excessive write cycles.
Innovation Solution
An enhanced copy-on-write method that writes new data to a new physical location on the SSD without physically moving the original data, using a storage virtualization layer to determine if a copy-on-write operation is needed and sending a command with arguments to map logical addresses to new physical locations, thereby reducing the number of I/O operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional copy-on-write technique is used to create snapshots on SSDs, then data consistency is maintained, but the number of write cycles increases excessively reducing SSD lifetime
Solution Approach 1:
The patent uses logical copying instead of physical copying. The snapshot volume maintains data consistency by copying logical address mappings rather than physically copying data blocks. When a write operation occurs on the production volume, the snapshot volume's mapping table is updated to point to the original data blocks, preserving data consistency without requiring physical data movement.
Solution Approach 2:
The patent introduces a mapping table as an intermediary layer between logical addresses and physical data blocks. This mapping table acts as a mediator that allows the snapshot volume to reference production volume data without direct physical copying. The mapping table updates enable the system to maintain data consistency while avoiding excessive write cycles to the SSD.
2Adaptability or versatility
If conventional copy-on-write technique is used, then snapshot functionality is achieved, but memory and bandwidth consumption increase significantly
Solution Approach 1:
The patent extracts the copy-on-write functionality from the physical data storage layer and relocates it to the logical mapping layer. By separating the snapshot creation logic from the physical data movement, the system achieves snapshot functionality while minimizing memory and bandwidth consumption. Only mapping table entries need to be updated rather than moving actual data blocks.
Solution Approach 2:
The patent implements logical copying of mapping information instead of physical copying of data. The snapshot volume creates a copy of the mapping table that references the same physical data blocks as the production volume. This approach provides full snapshot functionality while consuming minimal memory and bandwidth resources.
3Reliability
If conventional copy-on-write technique is used, then snapshot data consistency is maintained, but application write latency increases due to multiple I/O operations
Solution Approach 1:
The patent uses logical copying of mapping tables instead of physical data copying. When a snapshot is created or updated, only the mapping table entries need to be copied or updated, not the actual data blocks. This dramatically reduces the number of I/O operations required and decreases application write latency while maintaining snapshot data consistency.
Solution Approach 2:
The patent performs preliminary setup by creating the mapping table structure in advance. The mapping table is pre-configured with logical to physical address mappings, allowing snapshot operations to proceed efficiently by simply updating mapping entries rather than performing multiple data read/write operations.
Data Source
AI summary
A method for increasing the efficiency of a “copy-on-write” operation performed on an SSD to extend the life of the SSD is disclosed herein. In one embodiment, such a method includes receiving a first logical address specifying a logical location where new data should be written to an SSD. The first logical address maps to a first physical location, storing original data, on the SSD. The method further receives a second logical address specifying a logical location where the original data should be available on the SSD. The second logical address maps to a second physical location on the SSD. To efficiently perform the copy-on-write operation, the method writes the new data to a new physical location on the SSD, maps the first logical address to the new physical location, and maps the second logical address to the first physical location. A corresponding apparatus is also disclosed.