This case study documents the high-stakes restoration of a 25 GB MongoDB 4.x database after a catastrophic metadata failure. By bypassing the corrupted WiredTiger.wt control file, the AS Data Recovery team successfully extracted all collections directly from the physical storage layer.
Client & Data Information
- Client Name: Confidential
- Data Type: MongoDB 4.x (WiredTiger Storage Engine)
- Data Capacity: 25 GB
- Primary Issue: Synchronization Error / Write Corruption / “Code 100” Shutdown
- Specific Error: WiredTiger error (-31802) … unable to read root page from file:WiredTiger.wt
Incident Summary
The client’s MongoDB instance suffered a synchronization error during a high-load write operation, leading to immediate database instability. In an attempt to restore service, the client attempted a self-repair. However, the system failed to initialize, returning WiredTiger error -31802.
The logs confirmed that while the engine tried to recover from the last clean checkpoint, it hit a critical failure: it could not read the root page of the WiredTiger.wt file. Since this file acts as the master index for all collections, the database was effectively “blind” and could not identify or open its own data files.
Technical Analysis
Upon forensic analysis of the 25 GB data directory, AS Data Recovery engineers identified:
- Metadata Collapse: The WiredTiger.wt file, which maps logical collection names to physical .wt files, was corrupted at the block level.
- Failed Checkpoint Recovery: The engine’s attempt to roll back to a clean state failed because the checkpoint pointers themselves were within the corrupted root page.
- Physical Data Persistence: Despite the master index being lost, the individual collection-*.wt files containing the raw BSON documents remained physically intact on the storage media.
Recovery Solution
The recovery strategy utilized Collection-Level Physical Carving. Since the MongoDB service could not start due to the root page error, our engineers bypassed the WiredTiger engine entirely. Using proprietary forensic tools, we interacted directly with the individual collection files. We manually mapped the internal B-tree structures of each .wt file to extract the BSON (Binary JSON) records, rebuilding the database from the raw storage fragments.
Recovery Process
- Forensic Data Mirroring: Created a bit-for-bit clone of the 25 GB data directory to ensure a non-destructive recovery environment.
- Collection Identification: Utilized AS Data Recovery specialized tools to scan the raw .wt files, identifying collection headers and document schemas without the WiredTiger.wt index.
- BSON Document Extraction: Performed a deep-sector parse of each collection file, carving out individual BSON documents and validating their structural integrity.
- Database Re-assembly: Imported the extracted records into a fresh, clean MongoDB 4.x instance.
- Integrity Validation: The client verified the restored collections, confirming a 100% recovery of all deleted and corrupted data.
Recovery Results
- Recovery Integrity: 100% (All collections and documents fully restored)
- Recovered Volume: 25 GB
- System Status: Database fully operational on a new instance.
- Total Recovery Time: 2 Hours
Expert Reminder from AS Data Recovery: When you see a “WiredTiger.wt” root page error, do not continue trying to restart or repair the service. Repeated attempts can overwrite the very data fragments needed for recovery. Contact AS Data Recovery professionals immediately for emergency 24/7 NoSQL restoration. We guarantee 100% original recovery for specific failures, regardless of database size.