Storage Snapshot Write Delay Reduction via Segmentation
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Solution Overview
Problem
Existing data storage systems face delays in processing write operations during snapshot activation, as they require holding all write operations until snapshot metadata is updated, leading to increased latency with large numbers of logical storage units.
Innovation Solution
Implement a method where write operations are allowed to proceed while snapshots are being activated, with write operations being logged and processed after snapshot activation, allowing for reduced latency by suspending snapshot write processing and holding only necessary write operations until logged operations are processed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write operations are held until snapshot metadata is updated, then snapshot consistency is ensured, but write operation latency increases
Solution Approach 1:
The patent segments write operations into two categories: those that must be held (affecting snapshot data) and those that can proceed normally (not affecting snapshot data). This segmentation allows the system to maintain snapshot consistency for critical writes while allowing non-critical writes to continue without delay, thereby reducing overall write latency while preserving snapshot reliability.
Solution Approach 2:
The patent introduces an intermediary mechanism (snapshot write processing suspension and resumption logic) that mediates between the need for snapshot consistency and the need for write performance. The system temporarily suspends snapshot write processing only when necessary and resumes it afterward, acting as a buffer that reconciles the conflicting requirements of consistency and latency.
2Measurement precision
If all write operations are held during snapshot activation, then snapshot accuracy is improved, but system productivity decreases
Solution Approach 1:
The patent segments write operations based on their impact on snapshot accuracy. Only write operations that modify snapshot data are held during snapshot activation, while other write operations continue to be processed. This selective holding approach maintains snapshot accuracy for critical data while preserving system throughput for non-critical operations.
Solution Approach 2:
The patent applies partial action by holding only the necessary subset of write operations (those affecting snapshot data) rather than all write operations. This partial holding strategy achieves the required snapshot accuracy while minimizing the impact on overall system productivity, as the majority of write operations can proceed without interruption.
3Reliability
If write processing is suspended during snapshot activation, then data integrity is maintained, but operation speed decreases
Solution Approach 1:
The patent segments write processing into snapshot-affecting operations and non-snapshot operations. Only snapshot-affecting writes are suspended during snapshot activation to maintain data integrity, while non-snapshot writes continue at full speed. This segmentation preserves data integrity for critical operations while maintaining high write speeds for other operations.
Solution Approach 2:
The patent suspends write processing only partially and temporarily—specifically for snapshot-affecting operations during the snapshot activation window. This partial suspension maintains data integrity where needed while allowing the majority of write operations to proceed at normal speeds, thus minimizing the overall impact on write operation speed.
Data Source
AI summary
Snapshots are processed without holding all write operations while the snapshots are being activated. Rather than holding all write operations until snapshots are activated, write operations may be allowed to proceed. Snapshot write processing may be temporarily suspended while the snapshots are being activated, including snapshot metadata being updated, while write operations received while the snapshots are being activated are logged. After snapshots have been activated for all logical LSUs for which snapshots were instructed to be activated, the logging of write operations may be stopped, and the logged write entries processed to determine whether any of the logged write operations require updating snapshot information of any logical storage elements (LSEs) of the LSUs. While the logged write operations are being processed, any write operations received from a host for an LSE having a logged write operation may be held until the held operation, or all held operations are processed.