On-SSD Copy-On-Write Mapping to Reduce Power and Bandwidth
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Solution Overview
Problem
Data copy operations on storage devices like SSDs consume significant media endurance, power, and internal read/write bandwidth, and do not effectively save physical and logical capacity.
Innovation Solution
Implementing Copy-On-Write (COW) techniques that track indirection updates to copied data without duplicating it, by updating logical-to-physical (L2P) and physical-to-logical (P2L) tables, storing tokens, and sending acknowledgments before actual data copying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional data copy operations are performed on SSD, then data is duplicated from source to destination, but media endurance is consumed and power is used
Solution Approach 1:
The system performs preliminary actions by updating L2P table mappings and storing tokens before actual data copying occurs. This allows the copy operation to be logically completed and acknowledged to the host before physical data movement, reducing immediate power consumption while ensuring data integrity through subsequent copy-on-write triggers.
Solution Approach 2:
The patent introduces tokens and L2P table mappings as intermediary mechanisms that decouple the logical copy completion from physical data duplication. These intermediaries allow the system to track copy operations and trigger actual data copying only when necessary (e.g., on write operations), thereby reducing unnecessary power consumption.
2Reliability
If conventional data copy operations are performed on SSD, then data is duplicated, but internal read/write bandwidth is consumed
Solution Approach 1:
The system updates L2P table mappings and stores tokens as preliminary actions before actual data copying. This defers the bandwidth-intensive data movement operation until it is actually triggered by write operations, allowing the system to maintain copy functionality while preserving bandwidth for other operations in the meantime.
Solution Approach 2:
The patent implements dynamic data copying where the actual copy operation is postponed until triggered by write operations to the source or destination LBA. This dynamic approach allows the system to adapt bandwidth usage to actual needs rather than consuming bandwidth continuously during copy operations.
3Reliability
If conventional data copy operations are performed on SSD, then data capacity is used for duplication, but physical and logical capacity are not saved
Solution Approach 1:
The system performs preliminary L2P table updates and token storage without immediately duplicating data. This allows the logical copy to be completed while deferring physical data duplication, thereby preserving storage capacity until the copy-on-write trigger actually requires data movement.
Solution Approach 2:
The patent implements a logical copy mechanism through L2P table mappings rather than immediate physical copying. The actual data copying is triggered only when necessary (on write operations), and the system efficiently manages the copied data by tracking references in L2P tables, thereby optimizing capacity usage.
Data Source
AI summary
On-SSD-copy using Copy-On-Write (COW) techniques track indirection updates to the copied data without duplicating the data. In one example, a method involves receiving a copy command to copy data from a source LBA to a destination LBA. An entry in a logical-to-physical (L2P) table corresponding to the destination LBA is updated to refer to the same physical address as the source LBA's entry in the L2P table. Flags in the L2P table are updated to indicate that more than one LBA refers to the same physical address. After updating the L2P table and before copying the data, a token is stored to the storage device. After storing the token, but before copying the data, an acknowledgement can be sent to the host to indicate the copy command is complete. A subsequent write to either the source or destination LBAs trigger a copy of the data.