Virtual Provisioning Storage Track Reclamation
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Solution Overview
Problem
Current storage systems, particularly those using Count Key Data (CKD) devices, face challenges in efficiently reclaiming unused storage space in virtual provisioning environments, as existing methods struggle to detect and return track space to a thin storage pool when it is no longer needed, leading to inefficient resource utilization.
Innovation Solution
A method is introduced that identifies candidate tracks for reclamation by scanning and monitoring changes in virtually provisioned devices, marking them for erasure, and scheduling the reclamation process as a background task, utilizing a utility that executes a track erase command and returns marked tracks to a free track pool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage space is allocated to thin devices in virtual provisioning, then host visible capacity is increased, but storage space cannot be easily returned to the shared pool when no longer needed
Solution Approach 1:
The system performs preliminary actions by monitoring file system metadata changes and identifying candidate tracks for reclamation before they are actually needed. The reclamation process is triggered proactively when files are deleted or moved, rather than waiting for manual intervention or periodic checks.
Solution Approach 2:
The system establishes a feedback mechanism where the file system notifies the storage system of metadata changes (file deletions, moves). This feedback loop enables the storage system to automatically respond by reclaiming space, creating a closed-loop control system that continuously optimizes storage utilization.
2Quantity of substance
If utilities like SDelete are used to fill unused spaces with zeroes, then space reclamation becomes possible, but a large number of write I/Os are generated that impact the system
Solution Approach 1:
The invention extracts the reclamation trigger from the data content itself. Instead of requiring the data to be zeroed out (as with SDelete), the system extracts the reclamation opportunity from file system metadata events (deletions, moves). This separates the reclamation trigger from any write operations, eliminating the performance penalty.
Solution Approach 2:
The patent replaces the mechanical approach of writing zeroes to tracks (physical operation generating I/O) with a metadata-based detection system. The file system's metadata updates serve as the trigger, substituting a lightweight information-based mechanism for a heavy data-write mechanism.
3Quantity of substance
If all storage chunks are checked for reclamation, then unused space can be identified, but the process is complex and cannot detect space that is not filled with zeroes
Solution Approach 1:
The file system metadata acts as an intermediary that simplifies the reclamation detection process. Instead of directly examining storage chunks to determine if they are unused, the system uses the file system's metadata (which tracks file locations and status) as an intermediary indicator. This intermediary provides a simple, reliable signal for reclamation without requiring complex analysis of the actual data.
4Adaptability or versatility
If CKD devices are used for storage, then data architecture flexibility is improved, but no simple method is available to return track space to a thin storage pool
Solution Approach 1:
The system segments the reclamation process into distinct phases: monitoring phase (tracking file system events), identification phase (selecting candidate tracks based on events), and execution phase (performing reclamation). This segmentation allows the system to handle CKD device complexity in a structured way, addressing each aspect separately rather than attempting a monolithic solution.
Data Source
AI summary
A reclaim system provides for marking each track that is intended to be reclaimed in one or more storage devices and detecting and reclaiming such tracks. The reclaim system may include a feature and/or utility that may be used to mark, detect and return tracks to a free track pool of a virtual provisioning storage system in connection with the use of one or more thin Count Key Data (CKD) devices. Reclaim processing may include identifying tracks to be reclaimed, marking mark the tracks to be reclaimed, detecting tracks that have been marked to be reclaimed, and performing a reclaim task to return the marked and detected tracks to the free track pool, thereby reclaiming the tracks.