SSD LPT Restoration via Reverse Journal Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional NAND Flash-based SSDs face inefficiencies in updating logical to physical tables due to out-of-place writes and garbage collection processes, leading to unnecessary updates and increased write amplification, which affects performance and memory wear.
Innovation Solution
A method implemented by a controller to examine journal entries from recent to oldest, determining if LPT entries have already been updated, and discarding redundant updates to minimize unnecessary processing and memory wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If journal entries are processed sequentially from oldest to most recent to restore LPT entries, then all journal entries can be applied, but redundant updates increase write amplification and memory wear
Solution Approach 1:
The patent inverts the conventional processing order by examining journal entries from most recent to oldest instead of oldest to most recent. This reversal allows the system to apply only the necessary updates while automatically skipping redundant ones, as newer entries overwrite older updates to the same LPT entries. This inversion resolves the contradiction by maintaining restoration completeness while eliminating redundant writes that cause write amplification and memory wear.
2Reliability
If all journal entries are applied to restore LPT entries, then the LPT is fully updated, but unnecessary updates increase processing time and memory wear
Solution Approach 1:
By processing journal entries in reverse chronological order (most recent first), the patent enables the system to apply updates efficiently while skipping redundant ones. This approach maintains LPT entry accuracy because the most recent updates are applied first, and subsequent older updates to the same entries are automatically detected and skipped. The processing time is reduced because unnecessary write operations are eliminated, directly resolving the contradiction between accuracy and duration.
3Reliability
If redundant journal entries are processed, then all potential updates are attempted, but memory cell wear increases due to unnecessary write operations
Solution Approach 1:
The patent applies reverse chronological processing to eliminate redundant write operations that cause memory cell wear. By examining journal entries from most recent to oldest, the system ensures that only necessary updates are written to the LPT, as newer entries naturally supersede older ones. This approach maintains update completeness while significantly reducing the harmful effect of unnecessary writes on memory cell lifespan.
Solution Approach 2:
The patent converts the potential harm of processing redundant journal entries into a benefit by using the redundancy itself as a marker for skipping unnecessary updates. The presence of multiple updates to the same LPT entry in the journal is transformed from a waste of resources into an opportunity to optimize the restoration process, where the system can confidently skip older updates knowing that newer ones have already applied the necessary changes.
Data Source
AI summary
A controller-implemented method, according to one embodiment, includes: examining, by the controller, each of a plurality of journal entries from at least one journal beginning with a most recent one of the journal entries in a most recent one of the at least one journal and working towards an oldest one of the journal entries in an oldest one of the at least one journal, the journal entries corresponding to one or more updates made to one or more logical to physical table (LPT) entries of a LPT; determining, by the controller, whether a current LPT entry, which corresponds to a currently examined journal entry, has already been updated; and discarding, by the controller, the currently examined journal entry in response to determining that the current LPT entry has already been updated.