Cache Memory Partitioning for Data Reliability
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Solution Overview
Problem
Conventional memory sub-systems with a smaller number of cache memory devices struggle to implement high-reliability cache memory techniques due to insufficient discrete devices to effectively distribute data and reconstruct data using error correcting codes, leading to potential data loss in case of failures.
Innovation Solution
The memory sub-system partitions cache memory into a cache portion and a write buffer portion, where write data is stored in the cache portion and a duplicate copy is stored in the write buffer portion accessible via a different channel, allowing for data recovery in case of channel failures by using write buffer records to map locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional memory sub-systems use a smaller number of cache memory devices, then device complexity is reduced, but data reliability deteriorates due to insufficient devices for effective data distribution and error correction
Solution Approach 1:
The cache memory is segmented into two distinct portions: a cache portion for storing write data and a write buffer portion for storing duplicate copies. This segmentation allows the system to achieve data redundancy and reliability without requiring a large number of discrete cache memory devices, as the write buffer portion acts as an independent failure recovery mechanism.
Solution Approach 2:
The patent implements data copying by storing duplicate copies of write data in the write buffer portion. This copying mechanism provides redundancy that enables data recovery in case of channel failures or device failures, thereby improving reliability without proportionally increasing the number of discrete memory devices.
2Device complexity
If cache memory stores only write data in a single location, then device complexity is reduced, but data reliability deteriorates due to inability to recover from channel failures
Solution Approach 1:
The write buffer portion is prepared in advance to store duplicate copies of write data before failures occur. This preliminary action ensures that when channel failures or device failures happen, the system can immediately recover data from the pre-stored duplicates without needing complex real-time recovery mechanisms.
Solution Approach 2:
The write buffer portion serves as an intermediary between the cache portion and the final data storage. It acts as a buffer that receives duplicate copies of data and provides them for recovery operations, thereby enabling data recovery capability while maintaining a relatively simple overall cache memory structure.
3Reliability
If the memory sub-system uses write buffer records to map locations, then data recovery capability is improved, but device complexity increases due to additional mapping structures
Solution Approach 1:
Instead of using complex mapping structures, the patent uses write buffer records that store duplicate copies of the mapping information itself. This copying approach simplifies the recovery process, as the records contain all necessary location mapping data needed to reconstruct the cache memory state after failures.
Data Source
AI summary
Data is stored at a cache portion of a cache memory of a memory sub-system responsive to a request to perform a write operation to write the data. A duplicate copy of the data is stored at a write buffer portion of the cache memory. The cache memory is partitioned into the cache portion and the write buffer portion. An entry that maps a location of the duplicate copy of the data stored at the write buffer portion of the cache memory to a location of the data stored at the cache portion of the cache memory is recorded in a write buffer record.