Storage Server Data Restore via Clone Redirection
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Solution Overview
Problem
Existing data restore techniques from network storage systems, such as volume SnapRestore and single-file SnapRestore, face issues with non-deterministic restore times, downtime during restoration, and inefficient storage space usage, making them unsuitable for applications sensitive to downtime and storage-constrained environments.
Innovation Solution
A method and apparatus for restoring a data set from a persistent point-in-time image (PPI) that involves creating a clone of the data set and transparently redirecting I/O requests, allowing for immediate data servicing while the restore process occurs, and then splitting the clone to share blocks efficiently, reducing downtime and storage consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing restore techniques (volume SnapRestore or single-file SnapRestore) are used, then data can be restored from a Snapshot, but the restore process causes downtime during which I/O operations cannot be performed
Solution Approach 1:
The system performs preliminary actions by creating a clone of the data set from the Snapshot before the actual restore operation. This clone is created in advance and can be prepared while the original data set remains operational, allowing the restore to proceed without causing downtime to I/O operations.
Solution Approach 2:
The patent introduces a clone data set as an intermediary between the Snapshot and the original data set. The clone serves as a mediator that absorbs the restore operations, allowing I/O requests to be redirected to the clone during the restore process without affecting the original data set's availability.
2Reliability
If existing restore techniques are used, then data restoration can be performed, but storage space consumption increases by at least the size of the Snapshot
Solution Approach 1:
The system merges the clone data set with the original data set by redirecting I/O requests to the clone during the restore process. This merging allows the restore operation to utilize the clone's storage space rather than requiring additional space equal to the Snapshot size, thereby optimizing storage utilization.
Solution Approach 2:
The patent employs discarding and recovering by temporarily using storage space for the clone during the restore process, then recovering and reusing that space once the restore is complete. The clone can be discarded after successfully restoring the data, allowing the storage space to be recovered and reused.
3Adaptability or versatility
If single-file SnapRestore is used to restore a single file or LUN, then granular restoration is possible, but the restore time becomes non-deterministic depending on file size and layout
Solution Approach 1:
The system performs preliminary actions by creating the clone data set in advance with a predetermined structure that matches the Snapshot. This preliminary clone creation establishes a fixed restore path and methodology, making the subsequent restore time deterministic regardless of the actual file size or layout being restored.
Solution Approach 2:
The patent applies parameter changes by modifying the I/O request redirection parameters to point to the clone data set during restore. This parameter change enables the system to control the restore process flow through predefined parameters, ensuring deterministic restore times while maintaining the ability to restore at fine granularity levels.
Data Source
AI summary
A method of operating a storage server includes executing a process of restoring a data set in an active file system of the storage server from a persistent point-in-time image of a data set, and during the process of restoring the data set, servicing input/output requests directed at the data set by a client of the storage server.