Flash Memory Hash Table Implementation for Reduced Erasure
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Solution Overview
Problem
Conventional flash memory systems face performance and lifespan penalties due to the need for multiple reads and writes, and large-unit erasures, making it inefficient for processing large datasets and implementing data structures.
Innovation Solution
Implementing data structures in flash memory that allow for overwrites, using logical-OR operations and Compare-and-Swap calls to modify existing data without erasing entire pages, reducing the number of erasures and improving performance by writing only to existing pages when changing bits from 0 to 1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional data structures are used in flash memory, then data can be stored and accessed, but multiple reads and writes are required causing performance penalty
Solution Approach 1:
The flash memory system is segmented into data pages and hash table entries, allowing selective access and modification of individual entries without requiring access to entire pages or blocks, thereby reducing the number of read/write operations needed
Solution Approach 2:
The system performs preliminary actions by pre-allocating hash table entries with valid data structures and using invalidation bits to track modifications. This allows updates to be performed by simply changing the invalidation bit state rather than performing full read-modify-write cycles
2Adaptability or versatility
If small edits are performed in flash memory, then data can be updated, but the entire page must be copied forward causing performance and lifespan penalty
Solution Approach 1:
The hash table implementation allows local quality by enabling modification of individual hash table entries without affecting other entries or requiring page-level operations. Each entry can be independently updated by modifying only its specific location in the flash memory
Solution Approach 2:
The system uses partial action by implementing hash table entries that occupy only a portion of a flash memory page. This allows updates to be performed on individual entries rather than requiring operations on the entire page, reducing the scope of each update operation
3Quantity of substance
If pages are erased in flash memory, then space can be reused, but flash memory lifespan is reduced due to limited erase cycles
Solution Approach 1:
The system implements discarding and recovering by using invalidation bits to mark hash table entries as invalid rather than physically erasing them. Invalid entries are logically discarded and can be recovered by clearing their invalidation bits, avoiding physical erase operations and extending flash memory lifespan
Solution Approach 2:
The hash table entries are designed as disposable objects that can be easily invalidated and recreated. Instead of performing expensive erase operations on entire pages, the system creates new valid entries when needed, treating individual entries as short-lived objects that can be freely created and discarded
4Productivity
If hash tables are implemented in flash memory, then large datasets can be processed efficiently, but the structure complexity increases
Solution Approach 1:
The system uses parameter changes by representing hash table entries in a standardized format with fixed fields (key, value, invalidation bit). This parameterized approach simplifies the complex task of managing hash tables in flash memory by providing a uniform structure that can be systematically created, accessed, and updated
Data Source
AI summary
Systems and methods for managing content in a flash memory. Systems and methods for implementing hash tables in a flash memory are disclosed. A hash table may include a flat array or an array of buckets that are each associated with a linked list. Adding or removing entries from the hash table or from the linked list are achieved by performing an overwrite operation where possible to pointers affected by the table operation.