Slice Allocation Metadata Verification via User Space Drivers
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Solution Overview
Problem
Conventional metadata recovery tools in data storage systems often crash when encountering corrupted metadata, leading to system panics, unintended LUN outages, and the potential for corruption to spread across multiple LUNs, requiring systems to be taken offline, and may conceal slice allocation metadata corruption that spans different user objects.
Innovation Solution
A method and apparatus for verifying the consistency of slice allocation metadata by accessing drivers in kernel space from user space, identifying discrepancies on a per-file-system basis, and storing diagnostic information, which avoids system panics and allows for persistent output data storage, facilitating the recognition of inconsistencies between user objects and file systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional metadata recovery tools run in kernel space, then they can directly access and repair metadata, but they may crash causing system panics and require reboots
Solution Approach 1:
The patent introduces user space as an intermediary layer between the recovery tool and kernel space metadata. The recovery tool runs in user space and communicates with kernel drivers through standardized interfaces, preventing direct crashes in kernel space while maintaining metadata access and repair capabilities.
Solution Approach 2:
The patent segments the recovery process into separate user space and kernel space components. User space contains the recovery tool logic and metadata storage, while kernel space contains only the driver interfaces. This segmentation isolates failures to user space, preventing system-wide panics.
2Ease of repair
If conventional recovery tools make metadata changes, then they can repair corruption, but they may cause LUNs to unexpectedly go offline and spread corruption
Solution Approach 1:
The patent performs preliminary verification of metadata consistency before making any changes. The tool checks for corruption patterns and validates repair operations beforehand, ensuring that repairs do not inadvertently spread corruption to other LUNs or file systems.
Solution Approach 2:
The patent applies repairs locally to specific corrupted metadata structures rather than making broad changes. Each repair operation is targeted and isolated, affecting only the specific corrupted slice or file system entry, preventing corruption from spreading to other LUNs.
3Speed
If recovery tools run in kernel space, then they can access metadata quickly, but taking systems offline is often necessary to avoid changing metadata during user access
Solution Approach 1:
The patent uses user space as an intermediary that allows recovery operations to proceed without requiring kernel mode transitions or system shutdowns. The tool reads and writes metadata through user space file system interfaces, maintaining system availability while performing repairs.
4Difficulty of detecting and measuring
If recovery tools report results on per-LUN basis, then they provide detailed LUN-specific diagnostics, but they may conceal slice allocation metadata corruption that spans different user objects
Solution Approach 1:
The patent merges metadata verification across multiple LUNs and file systems into a unified check. By examining slice allocation metadata at the file system level rather than individual LUN level, the tool detects corruption that spans multiple user objects while still providing detailed per-LUN diagnostic information.
Data Source
AI summary
A technique for verifying the consistency of slice allocation metadata includes accessing, from user space of an operating system running on the data storage apparatus, a set of drivers running in kernel space of the operating system to obtain slice allocation metadata from the set of drivers, and identifying discrepancies in slice allocation metadata returned from the set of drivers on a per-file-system basis.