Cache Area Reservation for Storage Compression Bottlenecks
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Solution Overview
Problem
When the free capacity of a storage device is insufficient, dirty data accumulates in the cache memory, leading to performance deterioration and potential system failures.
Innovation Solution
A storage apparatus comprising multiple storage devices, a first memory, and a processor that configures storage device groups, manages cache areas, and performs data compression to optimize storage capacity, determining whether to reserve cache areas for write requests based on available storage device information and cache information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data compression is performed in the storage device to reduce storage capacity consumption, then storage capacity efficiency is improved, but the storage controller cannot utilize the freed space for additional writes
Solution Approach 1:
The patent introduces cache area management as an intermediary mechanism between the storage controller and compressing drive. The controller predicts compression ratios and reserves cache areas before writes occur, allowing it to plan writes to accounts that will exist after compression. This mediator (cache reservation system) bridges the gap between the controller's need to write data and the drive's compression process that consumes space.
Solution Approach 2:
The system performs preliminary actions by predicting compression ratios before data is compressed and stored. The controller calculates expected compression outcomes in advance and reserves cache areas accordingly, so that when compression occurs, the freed space is already accounted for in the write plan. This preliminary prediction and reservation prevents the loss of write capability that would otherwise occur.
2Quantity of substance
If the storage controller writes data up to the full capacity of the compressing drive, then storage capacity is fully utilized, but no further data can be written even though compression would create free space
Solution Approach 1:
The controller performs preliminary compression ratio prediction and cache reservation before executing write operations. By calculating expected compression outcomes in advance and reserving cache areas, the controller ensures that write operations can continue without interruption even as compression frees up space. This preliminary planning eliminates waiting time and maintains write continuity.
Solution Approach 2:
The system implements feedback through monitoring the actual compression ratios achieved versus predicted ratios. The controller adjusts future cache reservations based on actual compression performance, creating a closed-loop system that optimizes write capacity utilization over time. This feedback mechanism ensures continuous adaptation to maintain write operation continuity.
3Speed
If cache memory is used to buffer write operations, then write speed is improved, but dirty data accumulates when storage device free capacity is insufficient
Solution Approach 1:
The controller implements feedback by monitoring cache area usage and dirty data accumulation in real-time. When cache utilization reaches thresholds or compression ratios indicate insufficient free capacity, the system triggers destage operations to flush dirty data to storage devices. This feedback-based control prevents cache overflow and maintains system stability while preserving write speed benefits.
Solution Approach 2:
The system dynamically adjusts cache management strategies based on current storage device free capacity and compression performance. Cache reservation sizes and destage triggers are not fixed but adapt to changing conditions, allowing the system to maintain optimal write speed while preventing dirty data accumulation that would compromise reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents excessive dirty data accumulation in the cache memory, ensuring efficient data storage and maintaining system performance by effectively managing cache areas and storage device utilization.
Implementation Method 1
The storage device compresses the destaged data to convert the destaged data into compressed data
Data Source
AI summary
To prevent an excessive increase of a dirty data amount in a cache memory. A processor acquires storage device information from each of storage devices. When receiving a write request to a first storage device group from a higher-level apparatus, the processor determines whether a write destination cache area corresponding to a write destination address indicated by the write request is reserved. When determining that the write destination cache area is not reserved, the processor performs, on the basis of the storage device information and cache information, reservation determination for determining whether to reserve the write destination cache area. When determining to reserve the write destination cache area, the processor reserves the write destination cache area. When determining not to reserve the write destination cache area, the processor stands by for the reservation of the write destination cache area.