Slice Access Proxying During Storage Unit Data Evacuation
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Solution Overview
Problem
Existing data evacuation processes in dispersed storage networks face inefficiencies, including unnecessary resource usage and reduced availability due to the transfer of deleted slices and incomplete data during unit replacement, leading to unnecessary rebuilding and incorrect version checks.
Innovation Solution
Implementing proxying of slice access requests during data evacuation, where the replacement storage unit forwards read and write requests to the retiring unit until the data is fully transferred, thereby minimizing network usage and ensuring accurate data availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data evacuation transfers all slices including deleted ones, then data integrity is maintained, but network resources are wasted and evacuation time increases
Solution Approach 1:
The system performs preliminary actions by marking slices as deleted in the metadata before physical evacuation occurs. The retiring storage unit maintains these deleted slices locally and uses metadata flags to indicate their deleted status, allowing the replacement unit to skip transferring them during evacuation, thus saving time while maintaining data integrity through the metadata record.
Solution Approach 2:
The patent extracts deleted slices from the evacuation process by identifying them through metadata markers. The replacement storage unit receives information about which slices are deleted and excludes them from the transfer, taking out only the necessary active data slices while leaving deleted ones at the retiring unit until they are fully removed from the system.
2Speed
If replacement unit processes read requests locally during evacuation, then response time improves, but data availability is reduced for incomplete data
Solution Approach 1:
The patent introduces the metadata as an intermediary that coordinates read requests during evacuation. When the replacement unit receives a read request for data that is not yet fully transferred, it consults the metadata to determine whether the data is complete or still being evacuated, and routes the request appropriately to ensure data availability while maintaining fast response times.
Solution Approach 2:
The system dynamically adjusts request handling during evacuation based on the completion status of data transfer. The replacement unit can switch between processing requests locally when data is available and forwarding requests to the retiring unit when data is still being transferred, optimizing both response time and data availability throughout the evacuation process.
3Reliability
If version checks are performed on evacuated data, then data consistency is ensured, but incorrect version checks occur when data is incomplete
Solution Approach 1:
The metadata is prepared in advance with version information for all slices, including deleted ones. This preliminary version information allows the replacement unit to perform accurate version checks without waiting for complete data transfer, ensuring data consistency while avoiding incorrect version checks that would occur with incomplete data.
4Reliability
If all slices are transferred during evacuation, then complete data migration is achieved, but unnecessary rebuilding occurs for deleted slices
Solution Approach 1:
The patent extracts deleted slices from the evacuation process by using metadata to identify and exclude them from physical transfer. The replacement storage unit receives a list of deleted slices from the metadata and skips transferring them, achieving complete migration of only necessary data while eliminating unnecessary rebuilding operations for deleted slices, thus improving evacuation efficiency.
Data Source
AI summary
A method begins by a processing module receiving a checked write slice request from a requesting entity. The method continues by determining that locally stored encoded data slices do not include the requested encoded data slice. The method continues by identifying an alternate location for the requested encoded data slice. The method continues by determining whether the alternate location is associated with storage of the encoded data slice. The method continues when the alternate location is associated with the storage of the encoded data slice, by issuing a favorable checked write slice response to a requesting entity. The method can include facilitating transfer of the requested encoded data slice from the alternate location to the storage unit for storage.