Thinly Provisioned File System Metadata Recovery
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Solution Overview
Problem
Existing file server systems lack proactive detection and containment of faults, errors, and corruptions, especially in thinly provisioned logical volumes, which hinders quick and reliable recovery from disruptions.
Innovation Solution
A file server architecture that maintains three copies of metadata across slices of physical storage, with one copy in each slice, another in a root slice, and a third in a kernel mode database, enabling automatic error detection and correction through comparison and reconciliation, ensuring deterministic recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three copies of metadata are maintained across slices for redundancy, then reliability of recovery is improved, but device complexity increases
Solution Approach 1:
The patent maintains three copies of metadata (slice metadata) in different locations: one copy in each slice's slice mark, a second copy in the root slice's slice map, and a third copy in the kernel mode database. This copying strategy ensures that if one copy is corrupted or lost, other copies can be used for recovery, directly improving reliability while managing complexity through structured redundancy
Solution Approach 2:
The metadata is segmented and distributed across multiple locations rather than stored centrally. Each slice contains its own slice mark with metadata, the root slice has a slice map, and the kernel mode database maintains another copy. This segmentation provides fault isolation and enables independent verification of metadata integrity across different storage locations
2Reliability
If metadata is stored in multiple locations for fault tolerance, then reliability is improved, but loss of time increases due to comparison and reconciliation operations
Solution Approach 1:
The system performs preliminary actions by maintaining multiple pre-synchronized copies of metadata in different locations before faults occur. The slice marks, slice map, and kernel mode database all hold copies of the same metadata, so when a fault is detected, the system can immediately compare and reconcile these pre-positioned copies without needing to retrieve or regenerate them, reducing recovery time
Data Source
AI summary
A file server architecture decouples logical storage from physical storage and provides proactive detection and containment of faults, errors, and corruptions in a file system, in order to enable in place (online) and non-intrusive recovery. The file system is built upon a thinly provisioned logical volume, and there are stored three copies of the metadata defining the logical volume in order to provide quick, deterministic, and reliable recovery from a faulted system. A first copy of the metadata is distributed among all of the slices of physical storage allocated to the logical volume. A second copy of the metadata is stored in a root slice of the logical volume. A third copy of the metadata is stored separate from the slices of physical storage allocated to the logical volume.