Storage Controller Cache Area Redefinition for Tiered Storage
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Solution Overview
Problem
Conventional tiered storage systems face a trade-off between suppressing data transfers between tiers and maintaining input/output performance, as frequent data transfers can degrade access performance, and existing cache techniques fail to effectively manage data between upper and lower tiers.
Innovation Solution
A storage controller is implemented in a tiered storage system that includes a logical volume management unit, a tier management unit, and a cache controller, which dynamically divides the storage area into data and cache areas, allowing data to be transferred between tiers while minimizing physical data transfers by redefining cache areas as data areas when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data transfer between tiers is performed frequently to maintain input/output performance, then access performance is improved, but the number of data transfer input/output operations increases causing degradation of input/output performance
Solution Approach 1:
The patent introduces a cache area in the upper tier as an intermediary buffer between upper and lower tiers. When data is accessed in the lower tier, it is cached in the upper tier, allowing subsequent accesses to be served from the cache without frequent data transfers between tiers. This mediator approach maintains access performance while reducing the frequency of inter-tier data transfers.
Solution Approach 2:
The patent performs preliminary caching of data in the upper tier before actual access occurs. By proactively caching data that is likely to be accessed soon, the system prepares the data in advance in the upper tier, so when access is needed, it can be served quickly without triggering frequent data transfers from the lower tier.
2Productivity
If data transfer between tiers is suppressed to reduce data transfer input/output operations, then input/output performance is maintained, but access performance degrades due to increased access to lower tier
Solution Approach 1:
The cache area acts as a mediator that satisfies access requests without requiring data transfers from the lower tier. By serving data from the cache in the upper tier, the system maintains input/output performance while simultaneously providing fast access, eliminating the need to choose between the two conflicting goals.
3Speed
If cache area is used to store data from lower tier, then access performance is improved, but storage capacity of upper tier for actual data is reduced
Solution Approach 1:
The patent dynamically manages the cache area in the upper tier, allowing its size and contents to change based on access patterns. The cache area is not fixed but adapts to store data that is most likely to be accessed, optimizing the balance between access performance and storage capacity utilization.
Solution Approach 2:
The system changes the functional parameter of storage areas in the upper tier, designating certain areas as cache areas while maintaining the ability to reassign them as data areas when needed. This parameter change allows the same physical storage to serve dual purposes: caching for performance and data storage for capacity.
Data Source
AI summary
According to one embodiment, there is provided a storage controller for use in a tiered storage system. The tiered storage system includes a first storage device having the first physical volume of a first tier, and a second storage device having the second physical volume of a second tier lower than the first tier. The cache controller of the storage controller divides the storage area of the first physical volume into a set of data areas and a set of cache areas. The cache controller changes the first cache area of the first physical volume to a first data area, when first data to be transferred from the second physical volume to the first physical volume is also stored in the first cache area.