Storage Control Device Auxiliary Cache Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing storage devices face delays in accessing disks due to processing delays, particularly when caching fails, and the use of auxiliary cache memory does not adequately address the reliability concerns during power outages or failures, leading to prolonged write-back times and potential data loss.
Innovation Solution
A storage control device with an auxiliary cache memory, a volatile memory, and a processor that manages data by executing writing control processes, information management, and saving control processes, including stopping write operations to the disk, securing management information, generating copies, and writing data based on management information to ensure data integrity and reliability during failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacity of DRAM is significantly increased to improve cache hit ratio, then the cache hit ratio is improved, but the cost increases and the device becomes more complex due to requiring large-capacity battery
Solution Approach 1:
The memory system is segmented into three hierarchical layers: DRAM (first cache memory) for high-speed access, auxiliary cache memory (second cache memory) for intermediate storage, and disk storage for permanent storage. This segmentation allows each layer to perform its optimal function, with the auxiliary cache memory handling data that doesn't fit in DRAM, thereby improving overall cache hit ratio without requiring excessive DRAM capacity.
Solution Approach 2:
The auxiliary cache memory acts as an intermediary between DRAM and disk storage. When DRAM cache fails, data can be retrieved from the auxiliary cache memory before falling back to disk, reducing access delays. This intermediary layer improves reliability and cache performance without the complexity and cost of significantly expanding DRAM capacity.
2Speed
If auxiliary cache memory is used to improve reading speed, then the speed of processing for reading is improved, but write-back time increases when data needs to be written from auxiliary cache memory to disk
Solution Approach 1:
The system performs preliminary actions by writing data to the auxiliary cache memory in advance during normal operations. When a failure occurs, the management information already stored in the auxiliary cache memory enables rapid recovery and write-back operations, reducing the time penalty that would otherwise be incurred.
Solution Approach 2:
The system maintains copies of management information in both DRAM and auxiliary cache memory. This copying strategy allows the system to quickly access management information from the auxiliary cache memory during failure recovery, enabling faster write-back operations compared to retrieving management information from disk storage.
3Productivity
If auxiliary cache memory is used to improve writing performance by storing dirty data, then the cache region becomes available and writing performance is improved, but data reliability is compromised during power outages or failures
Solution Approach 1:
The system implements feedback mechanisms through management information that tracks the state of data in the auxiliary cache memory (clean vs. dirty). This feedback enables the system to make informed decisions about data recovery and write-back operations during failure scenarios, ensuring that dirty data is properly recovered while maintaining writing performance benefits.
Solution Approach 2:
Management information is copied to the auxiliary cache memory alongside data. This copying ensures that even if power is lost or a failure occurs, the management information survives in the non-volatile auxiliary cache memory, enabling reliable recovery of dirty data and maintaining both writing performance and data reliability.
4Speed
If management information is stored in DRAM for high-speed access, then auxiliary cache memory can be referenced at high speed, but management information is lost during power outages or failures
Solution Approach 1:
The system maintains copies of management information in both DRAM and auxiliary cache memory. The DRAM copy enables high-speed access during normal operations, while the auxiliary cache memory copy ensures survival during power outages or failures. This dual-copy strategy resolves the contradiction between speed and reliability.
Solution Approach 2:
The system prepares for potential failures by pre-storing management information in the non-volatile auxiliary cache memory before any failure occurs. This beforehand cushioning ensures that even if DRAM is lost during a power outage, the management information is already protected in the auxiliary cache memory, enabling rapid recovery without data loss.
Data Source
AI summary
A storage control device includes: an auxiliary cache memory that is a nonvolatile memory; a volatile memory; and a processor configured to execute a saving control process after a predetermined failure occurs, the saving control process being configured to (a) cause a writing control process to stop writing of data stored in the auxiliary cache memory to the storage medium, (b) secure, in the auxiliary cache memory, a storage region for storing the management information of the volatile memory, (c) generate a copy of management information of the volatile memory in the storage region, and (d) cause the writing control process to execute control to write first data stored in the volatile memory to the auxiliary cache memory or the storage medium based on the management information of the auxiliary cache memory.