Oldest Section Write Policy for Address Mapping Table Recovery
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Solution Overview
Problem
Current memory sub-systems face inefficiencies in power loss recovery due to the round robin policy, which results in inconsistent state reconstruction and high resource usage during journal evaluation and replay after a power loss event.
Innovation Solution
Implementing an oldest section write policy for the address mapping table, where the memory sub-system controller writes dirty entries to non-volatile memory based on a threshold journal count, sets flags to identify the oldest section, and replays journal entries starting from this section, reducing the need to read and evaluate all journal entries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If round robin policy is used for writing address mapping table sections, then all sections are written uniformly, but recovery time increases and resource usage increases due to evaluating all journal entries
Solution Approach 1:
The address mapping table is divided into multiple sections, each with its own oldest section indicator. This segmentation allows the system to focus recovery efforts on specific sections rather than processing the entire table, thereby reducing recovery time and resource consumption.
Solution Approach 2:
The system maintains oldest section indicators that track which section contains the oldest data before a power loss event occurs. This preliminary tracking enables the recovery process to immediately identify which sections need reconstruction without having to evaluate all journal entries, significantly reducing recovery time and computational resources.
2Reliability
If all journal entries are read and evaluated during power loss recovery, then complete state reconstruction is achieved, but resource usage and time consumption increase
Solution Approach 1:
The system extracts and tracks the oldest section identifier separately from the rest of the address mapping table. During recovery, only journal entries related to sections older than the tracked oldest section need to be processed, allowing the system to take out unnecessary evaluation of newer sections while maintaining complete state reconstruction for the critical older sections.
3Loss of energy
If dirty entries are written less frequently, then non-volatile memory write operations are reduced, but recovery complexity increases after power loss
Solution Approach 1:
The system uses oldest section indicators as feedback mechanisms that continuously track which section contains the oldest data. This feedback allows the controller to make informed decisions about which sections need to be written to non-volatile memory, balancing the frequency of write operations with the need to maintain recoverable state information without excessive complexity.
Data Source
AI summary
A journal count reflecting a number of logical-to-physical (L2P) journals written to a non-volatile memory device is maintained, wherein each L2P journal is associated with one or more updates to an L2P address mapping table. In response to determining that the journal count satisfies a threshold criterion, a first section of a plurality of sections of the L2P address mapping table is identified, wherein the plurality of sections of the L2P address mapping table is cached in a volatile memory device. The first section of the L2P address mapping table is written to the non-volatile memory device.