Cache-Based Logical Device Switching Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The LDEV jukebox function in storage systems causes frequent logical device switching, leading to performance deterioration and increased burden on the host system due to the inability to perform data I/O processing during switch processing, necessitating exclusive processing and resulting in overhead.
Innovation Solution
An information processing apparatus and method that includes a storage apparatus with a first processing unit for dynamic mapping of logical devices to virtual logical units and a file sharing server with a cache memory to manage mapping relationships, allowing data I/O processing to occur in the cache memory, thereby reducing the frequency of logical device switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LDEV jukebox function dynamically switches the logical device allocated to the logical unit according to application program requests, then the storage system can handle logical devices in quantity exceeding OS management capacity, but frequent switch processing occurs when multiple application programs request different logical devices, causing performance deterioration and overhead
Solution Approach 1:
The system pre-loads data from the logical device into the cache memory before the application program actually needs it. When a logical device is allocated to a logical unit, the system proactively reads data into cache, so that subsequent data access can be served from cache rather than requiring immediate device switching. This preliminary action eliminates the performance penalty of dynamic switching by preparing data in advance.
Solution Approach 2:
The cache memory acts as an intermediary layer between the logical unit and the logical device. Instead of directly switching logical devices in response to application requests, the system uses the cache to buffer data, allowing multiple applications to share cached data without requiring frequent device re-allocation. This intermediary buffer decouples the application's data access needs from the physical device switching operations.
2Reliability
If exclusive processing is implemented to prevent logical device switching during host system access, then data access consistency is maintained, but the burden on the host system becomes significant
Solution Approach 1:
The cache memory serves as an intermediary that absorbs the complexity of device management away from the host system. The storage system's controller handles device switching and cache management independently, allowing the host system to access data through the cache without being burdened by exclusive processing requirements. This separates the reliability concerns of consistent access from the complexity of device switching management.
Solution Approach 2:
The storage system performs device allocation and cache management autonomously without requiring host system intervention. The controller automatically manages which logical device is allocated to which logical unit and when data should be cached, eliminating the need for the host system to implement complex exclusive processing logic. The system serves itself by handling device switching transparently.
Data Source
AI summary
An information processing system having a storage apparatus and a file sharing server. The storage apparatus comprises a plurality of storage devices for providing logical devices to store data; and a first processing unit for providing virtual logical units based on a mapping relation between the logical devices and the virtual logical units and being operative to switch the mapping relation dynamically according to an external request. The file sharing server comprises a cache memory including cache extents and a second processing unit controlled to provide the virtual logical units of the storage apparatus to a host system by using the cache extents, managing the mapping relation between the logical devices and the virtual logical units. The mapping between a logical unit and a logical device is dynamically switched as the logical devices store data provided from the host system according to external requests.