Online Cache Device Reduction via Labeling and Data Migration
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Solution Overview
Problem
Existing data storage systems face challenges in efficiently reducing cache devices without affecting performance, as traditional methods require destroying and rebuilding the cache, leading to data loss and prolonged downtime, which impacts overall system performance.
Innovation Solution
A method and apparatus for online reducing cache devices by keeping both cache devices in an enabled state, labeling one as a to-be-reduced device, removing cached data and IO historical information, and disconnecting it from the cache, allowing for seamless transition and minimal performance impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional cache reduction method is used (destroying and rebuilding cache), then cache device can be reduced, but system performance deteriorates due to data loss and prolonged downtime
Solution Approach 1:
The system performs preliminary actions by marking the first cache device as a to-be-reduced device before actual removal, blocking new data pages from being promoted to it. This preparatory step allows for controlled data migration and ensures the cache can continue serving IO requests during the transition, avoiding performance degradation.
Solution Approach 2:
The patent introduces an intermediary state (to-be-reduced device) that acts as a mediator between the active cache and complete removal. The marked cache device continues to serve IO requests while data is gradually migrated away from it, enabling smooth transition without disrupting system performance.
2Device complexity
If cache device is removed from cache, then cache complexity is reduced, but data availability worsens due to potential data loss
Solution Approach 1:
Before removing the cache device, the system performs preliminary data migration by blocking new data pages from being promoted to the marked device and gradually migrating existing data to other cache devices. This ensures data availability is maintained throughout the reduction process.
Solution Approach 2:
The marked cache device continues to serve IO requests during the migration process, maintaining continuous data availability. The system ensures that both reading and writing operations can still access data through the marked device until migration is complete, preventing any data unavailability.
3Quantity of substance
If cache device reduction process is performed, then storage cost is reduced, but time consumption increases due to prolonged downtime
Solution Approach 1:
The cache system maintains continuous operation throughout the reduction process. The marked cache device continues to serve IO requests, and data migration occurs in the background without requiring system downtime. This eliminates the prolonged downtime associated with traditional cache destruction and rebuilding methods.
Solution Approach 2:
The system performs preliminary marking and blocking operations that enable gradual data migration while the cache remains operational. This allows the reduction process to occur online without interrupting service, significantly reducing time loss compared to offline reconstruction methods.
Data Source
AI summary
The present disclosure provides a method and apparatus for online reducing cache devices from a cache. The cache includes a first cache device and a second cache device, the method comprising: keeping the cache and the second cache device in an enabled state; labeling the first cache device as a to-be-reduced device so as to block a new data page from being promoted to the first cache device; removing a cached data page from the first cache device; removing the cached input output (IO) historical information from the first cache device; and removing the first cache device from the cache. There is also provided a corresponding apparatus.