Storage System Write Logging for Reliable Power-Loss Recovery
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Solution Overview
Problem
Existing storage systems experience decreased I/O performance due to multiple writes required for data updates, which can lead to errors during power loss, affecting data reliability and consistency.
Innovation Solution
Implementing a storage system with a cache area for temporary data storage, a cache log storage area for updated content, a data storage area for permanent data, and a write log storage area, allowing for write-back or write-through operations to optimize data handling and reduce the number of writes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the storage system writes updated content to the storage device in advance and then performs update, then data reliability is improved, but the number of drive writes increases and I/O performance deteriorates
Solution Approach 1:
The patent applies preliminary action by writing updated content to the storage device in advance before actual data update occurs. The write log stores the updated content beforehand, so that if power is lost during the update process, the data can be recovered using the pre-written updated content from the write log, thus ensuring data reliability without requiring multiple write operations during critical moments
Solution Approach 2:
The patent uses copying by creating a write log that contains a copy of the updated content separately from the main data storage. This write log acts as a backup copy that can be used for recovery purposes, allowing the system to maintain data reliability while optimizing the main data update process to minimize the number of write operations affecting I/O performance
2Reliability
If the storage system performs multiple writes for data update, then data reliability is improved, but the processing time increases
Solution Approach 1:
The system performs the write operation preliminarily by storing updated content in the write log before the actual data update. This preliminary write ensures that even if power is lost during the update process, the data consistency can be restored using the pre-prepared updated content, thereby maintaining data reliability while reducing the need for multiple write operations during the update process
Solution Approach 2:
The write log acts as an intermediary between the cache area and the data storage area. It stores the updated content that can be used to recover data consistency if power is lost, serving as a mediator that ensures data reliability without requiring multiple direct write operations between the cache and data storage areas, thus reducing processing time
Data Source
AI summary
When execution of a write-back operation is selected, a storage system stores, in a cache area, data for which a write request is issued from a higher-level apparatus, stores an updated content of the cache area in a cache log storage area, and then writes the data to a data storage area. On the other hand, when execution of a write-through operation is selected, the storage system does not execute storage into the cache area and the cache log storage area, stores an updated content of the data storage area in a write log storage area, and then writes the data to the data storage area.