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Sync Synology NAS with Google Drive Without Data Loss: A Compare-First Strategy

· 4 min read
Tayson
Tayson
Senior Engineer

NAS-to-cloud sync is powerful, but one wrong direction can delete everything. A Compare-first workflow makes NAS sync predictable and safe.

Synology NAS + Google Drive (or OneDrive) is the most common small business and home setup. The problem is that sync feels easy until a wrong direction, a cleanup in the cloud, or a timing mismatch causes massive deletions. This guide shows how to keep sync safe with a Compare-first strategy in RcloneView.

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Manage & Sync All Clouds in One Place

RcloneView is a cross-platform GUI for rclone. Compare folders, transfer or sync files, and automate multi-cloud workflows with a clean, visual interface.

  • One-click jobs: Copy · Sync · Compare
  • Schedulers & history for reliable automation
  • Works with Google Drive, OneDrive, Dropbox, S3, WebDAV, SFTP and more
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NAS is the local source of truth. Cloud services add sharing and off-site protection. But sync is unforgiving:

  • A wrong direction wipes the destination
  • A cleanup in one side deletes the other
  • NAS file semantics do not match cloud API behavior

That is why searches like "synology google drive sync delete" or "nas cloud sync problem" are so common.

DSM Cloud Sync is simple, but limited​

DSM Cloud Sync is convenient, yet it lacks critical safety controls:

  • No clear preview of deletions
  • Limited filtering of NAS system files
  • Fewer guardrails for large migrations

If you need more control, you need Compare-first workflows.

Why Google Drive and OneDrive are especially risky​

  • Google Drive uses a virtual file structure and API-based metadata.
  • OneDrive introduces conflict files and lock behaviors.
  • NAS expects local file semantics and immediate updates.

These differences amplify sync mistakes unless you validate changes first.

The core problem: blind sync​

Blind sync means you hit Sync without seeing what will change. Typical accidents:

  • Empty NAS folder -> sync -> cloud deletes everything
  • Cloud cleanup -> sync -> NAS deletes everything

Compare-first eliminates this risk by showing the changes before they happen.

Compare vs Sync: different purposes, different risks​

  • Compare is read-only and safe. It shows what will change.
  • Sync makes real changes that are hard to reverse.

Compare is not optional. It is the safety gate.

Compare results filters

Step-by-step: safe NAS -> Google Drive / OneDrive sync​

Step 1: define the scope​

  • Do not sync the entire NAS volume
  • Pick specific shared folders
  • Separate by team or project

Step 2: decide direction first​

  • NAS -> Cloud for backup
  • Cloud -> NAS for restore
  • Two-way sync is the most dangerous

Step 3: Compare before every Sync​

Check for:

  • large delete counts
  • unexpected file count changes
  • timestamp or size mismatches
Folder comparison completed

Copy first, sync later (the safer path)​

Copy is safer because it does not delete. Use Copy to validate the workflow before running Sync.

Compare and copy only changes

Once the structure is stable, consider Sync with Dry Run:

Sync dry run

Handle NAS system files during sync​

NAS directories often include:

  • @eaDir
  • temp caches
  • package-generated metadata

These files change frequently and cause repeated sync triggers. Use Compare and filters to exclude them.

Compare-first reduces cost and risk​

  • Less API traffic
  • Faster sync cycles
  • Predictable cloud usage
  • Fewer accidental deletions

Automate safe sync jobs​

Save the workflow as a Job and schedule it:

Save sync to JobsAdd job scheduling

This gives you repeatable settings, history logs, and easier audits.

Real-world NAS sync scenarios​

Home NAS photo backup​

  • NAS -> Google Drive
  • Compare + Copy-first

Office file server​

  • NAS -> OneDrive
  • One-way strategy, filter system files

Hybrid workflow​

  • NAS -> Cloud for backup
  • Cloud -> NAS for selective restore

Common myths​

"Two-way sync is always best." Convenient, but most dangerous.

"DSM Cloud Sync is enough." Works for simple cases, breaks at scale.

Best practices checklist​

  • Always Compare before Sync
  • Start with Copy
  • Keep scope small
  • Watch delete counts
  • Filter NAS system files

Conclusion: sync is safe if you Compare first​

NAS + Google Drive or OneDrive is powerful, but only if you control the workflow. Compare-first makes sync safe, predictable, and reversible. Confirm, copy, then sync.