Storage Controller Cache Data Log Drive Selection
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Solution Overview
Problem
Existing storage apparatuses face challenges in balancing high reliability with cost and performance, particularly in methods like RAID 6 where response times are long due to frequent drive access, and in log-based methods where drive bottlenecks can occur.
Innovation Solution
A storage apparatus with multiple kinds of non-volatile drives and controllers that generate cache data logs including memory data and headers, and selectively store these logs in drives based on necessary performance requirements, using a memory data protection function to manage log storage locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the write-through method is used to ensure high reliability, then data protection is improved, but response time deteriorates due to frequent drive access
Solution Approach 1:
The invention segments data protection into two parts: critical metadata (log head information such as sequence numbers and addresses) is written to the drive through write-through, while the actual data content is written to the drive through write-back. This segmentation allows the system to ensure reliability for critical recovery information without sacrificing overall response time.
Solution Approach 2:
The invention introduces an intermediary mechanism where log head information acts as a mediator between the cache and the drive. By writing this compact metadata to the drive, the system creates a reliable anchor point that enables data recovery without requiring the entire data set to be written through, thus improving response time while maintaining reliability.
2Loss of time
If log-based data protection is used to reduce drive access, then response time is improved, but drive bottleneck occurs due to large data volume
Solution Approach 1:
The invention extracts only the essential log head information (sequence numbers, addresses, and other metadata) from the complete log data and writes this extracted subset to the drive. By taking out only the critical portion needed for data recovery, the system reduces the volume of data requiring drive access, thereby eliminating the drive bottleneck while maintaining response time improvements.
Solution Approach 2:
The invention applies partial action by writing only the necessary log head information to the drive rather than the complete log data. This partial writing approach is sufficient to enable data recovery while avoiding the excessive drive access that would cause performance bottlenecks.
3Reliability
If RAID 6 is used to enhance reliability, then data protection is improved, but response time deteriorates due to multiple drive accesses for parity calculation
Solution Approach 1:
The invention segments the data protection function so that only log head information is written to the drive with full redundancy, while the actual data content uses simpler write-back without extensive parity calculations. This segmentation reduces the frequency and volume of drive accesses required for maintaining reliability.
4Productivity
If high-speed SSDs are used to store logs and avoid bottlenecks, then drive performance is improved, but cost increases
Solution Approach 1:
The invention uses a cost-effective approach by writing only small log head information to the drive rather than storing complete log data. This allows the use of standard, lower-cost drives instead of expensive high-speed SSDs, as the reduced data volume and frequency of writes make cheaper storage media sufficient for the task.
Data Source
AI summary
A controller has a memory data protection function of generating a cache data log including data of a memory and a header related to update of the data and writing the cache data log to any one of a plurality of kinds of drives, and the controller uses the memory data protection function to select, from the plurality of kinds of drives, a drive that is to store the cache data log, according to necessary performance, and store the cache data log in the selected drive.