Storage Controller Slice Release for Snapshot Response
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Solution Overview
Problem
In Thin Provisioning storage systems, the asynchronous execution of copying and releasing processes due to initialization commands leads to delayed responses and performance degradation, particularly when creating snapshots of logical volumes.
Innovation Solution
A storage system with a controller that receives write requests, generates slices from a storage pool, updates a slice table, and releases slices upon duplicating data to a copy target volume, allowing for immediate response to release commands while background copying occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the copying process and releasing process are performed asynchronously in response to initialization commands, then the system can handle snapshot creation more flexibly, but the response process is delayed and performance is degraded
Solution Approach 1:
The patent segments the releasing process into two independent parts: (1) releasing the logical volume from the host's perspective, and (2) releasing the physical disk resources after copying completes. This allows the host to receive immediate confirmation while the background copying continues asynchronously, resolving the contradiction between flexibility and response time.
Solution Approach 2:
The patent performs preliminary actions by initiating the copying process before the releasing process completes. The copying starts in advance and runs in the background, while the logical volume is released immediately to satisfy the host's request, thus improving response time without sacrificing snapshot creation flexibility.
2Loss of substance
If the entire logical volume is initialized to release allocated physical volume, then physical resources are freed, but the process requires larger I/O ranges and increases processing overhead
Solution Approach 1:
The patent applies local quality by allowing different portions of the logical volume to be released at different times. Specifically, the logical volume structure is released immediately while physical disk resources are released only after copying completes. This selective, staged approach reduces the initialization command range required compared to traditional all-or-nothing initialization.
Solution Approach 2:
The patent introduces dynamic behavior where the releasing process adapts based on copying progress. The system dynamically transitions from holding physical resources during active copying to releasing them upon completion, allowing flexible resource management without requiring large initialization ranges upfront.
Data Source
AI summary
A storage system has a storage pool for at least one of a logical volume having a plurality of slices, a memory for storing a slice table indicating whether each slices of the logical volume is assigned from the storage pool or not, and a controller for receiving a release command for releasing one of the slices, sending out a response indicating the releasing of one of the slices corresponding to the release command has completed regardless of an execution of processing corresponding to the release command, duplicating a copy target area included in the one of the slices corresponding to the release command into a copy target volume included in the storage pool, and releasing the one of the slices upon completely duplicating the copy target area into the copy target volume.