D3V’s Engineering-First Approach to Zero-Loss Document Migration

The client undertook a large-scale document migration to move approximately 50,000 critical land, legal, and operational documents from Quorum software to legacy SFTP servers and GCE-hosted storage into Google Workspace Shared Drives.

The primary objective was not just data movement, but migration accuracy, audit readiness, and long-term manageability.

By combining high-throughput transfer tooling with custom-built validation and reconciliation scripts, the project delivered a provably complete and reliable migration with zero silent data loss.

Business & Technical Requirements

The migration was driven by both operational and compliance needs:

• Centralize documents in Google Shared Drives
• Preserve deeply nested folder structures
• Handle large file volumes (~50k files) efficiently
• Support restartable and resilient transfers
• Provide script-based validation and reconciliation
• Maintain security, traceability, and audit confidence

Source & Target Environment

Source Systems

• From Secure SFTP server
• To Google Compute Engine VM with attached persistent disks

Target Platform

• Google Workspace Shared Drives

Tooling Stack

• rclone for file transfer
• Custom Python scripts for validation
• Google Drive APIs

Migration Strategy

The migration leveraged rclone for its performance, reliability, and Google Drive compatibility.
Transfers were optimized using controlled concurrency, detailed logging, and resumable operations to safely handle interruptions and retries.

The folder hierarchy was recreated exactly in Shared Drives, ensuring business users experienced no structural change post-migration.

Validation & Reconciliation Approach

To eliminate assumptions, the project relied on script-driven validation rather than UI-based checks.

Custom Python scripts were developed to reconcile files between source and destination using five key matching rules:

• Exact path matching
• Filename-only matching
• Case-insensitive normalization
• Special character normalization
• Size and checksum verification (where applicable)

This multi-rule approach handled real-world inconsistencies between filesystems and prevented false mismatches.

Handling Scale & Edge Cases

Given the volume and complexity of the data:

• Source and destination inventories were normalized and sorted
• Line-by-line comparisons were used to detect drift
• Missing, extra, and duplicate files were isolated into audit reports
• Selective re-migrations were performed only where required

This ensured efficient resolution without reprocessing the entire dataset.

Security & Audit Readiness

Security and governance were integral to the migration:

• Least-privilege access to Shared Drives
• No destructive operations on source systems
• Detailed logs and reconciliation outputs preserved
• Clear traceability from source files to destination objects

This ensured the migration could withstand internal and external audits.

Outcomes & Results

• Successfully migrated ~50,000 documents
• Preserved full folder hierarchy
• Achieved zero unexplained discrepancies
• Delivered script-backed validation evidence

Key Learnings

• Enterprise migrations require verification, not trust
• Filesystem normalization is essential at scale
• Custom scripts bridge gaps left by off-the-shelf tools
• Audit readiness must be designed, not added later

Conclusion

The migration demonstrates a disciplined, engineering-first approach to enterprise document modernization.

By prioritizing validation and reconciliation alongside transfer speed, the project delivered a migration that is complete, defensible, and future-ready.