File System Fault Tree for Inline Metadata Recovery
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Solution Overview
Problem
Conventional file system recovery tools are inefficient as they often require taking the entire file system offline, leading to increased recovery time and exacerbated inconsistencies, as they wait for metadata errors to cause a crash before initiating recovery.
Innovation Solution
The improved technique involves creating a fault tree to isolate and classify errors for inline recovery, using shallow consistency checks and CRC checks to identify and repair metadata inconsistencies without taking the entire file system offline, allowing for online recovery of non-fatal errors and offline recovery during maintenance windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional file system recovery tools are used to repair metadata errors, then the file system can be restored to a consistent state, but the entire file system must be taken offline resulting in extended data unavailability
Solution Approach 1:
The patent divides the file system into hierarchical metadata objects and creates a fault tree structure that segments the recovery process. Instead of recovering the entire file system, only the specific faulty metadata objects and their dependent objects are isolated and recovered. This segmentation allows the rest of the file system to remain online and operational during recovery operations.
Solution Approach 2:
The patent extracts the faulty metadata objects from the overall file system operation by creating a fault tree that identifies and isolates specific fault branches. The faulty objects are taken out of the active file system operations and recovered separately, allowing the main file system to continue functioning while only the affected portions are taken offline for repair.
2Reliability
If recovery is delayed until metadata errors cause a file system crash, then conventional recovery tools can be executed, but the recovery time increases due to the exacerbation of inconsistent metadata
Solution Approach 1:
The patent implements preliminary consistency checking actions that continuously monitor metadata objects for errors before they cause a file system crash. When inconsistencies are detected, the fault tree is created and recovery is initiated immediately, preventing the exacerbation of errors that would occur if recovery were delayed until a crash. This preliminary detection and immediate response significantly reduces recovery time.
3Reliability
If the entire file system is taken offline for recovery, then all metadata objects can be repaired, but non-fatal errors in other branches unnecessarily contribute to system downtime
Solution Approach 1:
The fault tree structure segments the file system into independent branches based on metadata object dependencies. When an error is detected, only the specific fault branch containing the erroneous objects and their dependents is isolated for recovery. Other branches that are not affected by the error remain online and operational, eliminating unnecessary system downtime while ensuring consistency in the affected areas.
4Loss of time
If shallow consistency checking and fault tree creation are implemented for inline error recovery, then recovery time is reduced and non-fatal errors can be handled online, but the device complexity increases
Solution Approach 1:
The patent introduces a fault tree as an intermediary data structure that mediates between error detection and recovery execution. The fault tree automatically maps metadata object dependencies and enables the system to identify and isolate only the necessary objects for recovery. This intermediary structure automates the complexity of dependency analysis, making the recovery process more efficient without requiring complex manual intervention, thereby reducing recovery time while managing device complexity through automation.
Data Source
AI summary
A storage processor isolates and classifies file system faults and inconsistencies to produce a fault tree for inline error recovery. The storage processor isolates the metadata objects or objects that have internal inconsistencies, the storage processor creates a fault tree to map the file system; or portion of the file system with the errors or inconsistencies and the metadata objects dependent upon those objects. Once the fault having been mapped, determine the complexity of recovering the branch of the fault tree with the error. If the error is not too complex, performing recovery of the metadata objects online otherwise taking the system offline for file system recovery.