Incremental Sync Backup (-isync option)

What is Incremental Sync Backup?

Incremental Sync Backup is an advanced backup method that combines the traditional incremental backup approach with full directory structure preservation, selective storage of changed files, and link-based deduplication.

Executed via the -isync option, this method backs up only modified files while maintaining the complete directory structure, enabling straightforward full restoration.

In addition, no need to merge multiple incremental sets—a single snapshot of an incremental sync backup allows for quick and intuitive point-in-time recovery of specific directories or files.

Key Advantages

Sync-based Incremental Backup: Only changed files are copied, but the full directory structure is preserved.
Link-based Deduplication: Unchanged files are referenced using links from the previous backup to save disk space.
Single Point-in-Time Partial Recovery: Enables fast and intuitive recovery of specific files or directories at a desired point in time, without the need to reconstruct from multiple incremental backups.
Fast Backup Performance: Since only modified files are copied, backup time is significantly reduced.
Simple Restoration: Restoring data is as easy as copying the backup folder of the desired point in time.

Recommended Use Cases

Environments where data is constantly being updated, such as web servers, file servers, and database servers
Systems that require frequent backups
Scenarios where system load and network traffic during backup must be minimized
Storage cost-conscious environments that need to reduce redundant data storage
Situations that demand rapid recovery to a specific point in time

Command Usage

Full Backup – Initial Base Snapshot

./fbmega -isync -base [source_path] [backup_path]

Copies the entire source directory to the backup path, creating the initial reference point for future incremental sync backups.

Incremental Sync Backup

./fbmega -isync [reference-path] [source_path] [backup_path]

Compares the reference-path with the source path and stores only the changed files in the backup_path.

Unchanged files are referenced via links to the reference-path, greatly optimizing storage.

Example Backup Structure

  /backup/
  ├── 2025-06-01-base/ # Initial full backup (base)
  ├── 2025-06-02/ # Incremental sync backup 1 (changes from base + links)
  ├── 2025-06-03/ # Incremental sync backup 2 (changes from 06-02 + links)

Each incremental backup directory includes only the files that changed since the reference-path, and unchanged files are linked.
Users can browse the full directory at any backup point as if it were a complete backup.