DB-유

Synology Cloud Sync with Google Drive and Dropbox

· synology, cloud, backup

Colleagues kept dropping files into a shared Dropbox that nobody backed up, and I wanted an off-site copy of my own documents that didn't cost anything extra. Cloud Sync handles both. I pull the Dropbox down onto the NAS so it gets backed up with everything else, and push an encrypted copy of important folders up to Google Drive. The choices that matter are sync direction and encryption.

You need DSM 6.0 or later with Cloud Sync installed, working outbound internet, and a browser for the OAuth login. Watch the cloud quota too; Google Drive's free 15 GB fills fast.

Connecting the account

Open Cloud Sync, click the plus icon, and pick the provider. For Google Drive and Dropbox the package opens a browser window to the provider's login page; approve the request and you are returned to DSM with the account connected. Business accounts (G Suite, Dropbox Business) work the same way; Dropbox Business asks whether to connect the team or the member folder.

Task 1: pull a shared Dropbox onto the NAS

After connecting Dropbox, the task settings page appears:

  • Connection name: Dropbox - team share.
  • Local path: create or pick a shared folder, for example /cloudsync/dropbox.
  • Remote path: pick the shared folder inside Dropbox rather than the root, or you will sync the whole account.
  • Sync direction: "Download remote changes only".
  • Data encryption: off (files must stay readable on the NAS).
  • Schedule settings: leave continuous.

"Download remote changes only" means the NAS never uploads and never deletes in Dropbox, so an accidental deletion on the NAS does not propagate. Under Advanced settings, untick "Don't remove files in the destination folder when they are removed in the source folder" only if you want NAS-side deletions to mirror Dropbox deletions. For an archive I leave it ticked, so files deleted in Dropbox remain on the NAS.

Also under advanced settings you can filter by file size and by extension; excluding .tmp and ~$* Office lock files avoids churn.

Task 2: push an encrypted copy to Google Drive

Connect Google Drive, then:

  • Local path: /documents.
  • Remote path: create a folder in Drive, for example NAS-encrypted.
  • Sync direction: "Upload local changes only".
  • Data encryption: on. Set a strong password and download the .key file when prompted; keep both outside the NAS.
  • Advanced: tick "Don't remove files in the destination folder when they are removed in the source folder" so a deletion on the NAS does not wipe the cloud copy.

With encryption on, filenames and contents are encrypted with AES-256 before upload. Google sees only random-looking names and blobs. The downside is you cannot open the files in the Drive web interface; recovery requires Cloud Sync on a Synology, or Synology's Cloud Sync Decryption Tool for Windows and Mac, together with your password or key file.

Set a schedule if the upload competes with users during the day: Schedule settings → set a grid of allowed hours. Also consider Control Panel → Network → Traffic Control to cap Cloud Sync's upload.

Polling and concurrency

In Cloud Sync → Settings, "Polling period" controls how often the NAS checks the provider for changes when the provider does not push notifications. For Dropbox the package uses long polling; for Google Drive the default 60 seconds is fine. Increasing "Maximum concurrent upload files" helps with many small files; decreasing it helps on a weak upstream.

Testing both directions

The task's Overview shows Up to date once the initial sync finishes, with counts of synced files. Then test each direction:

  • Drop a file into the shared Dropbox from a laptop; within a minute it appears in /cloudsync/dropbox in File Station. Delete a file on the NAS side and confirm it is not deleted in Dropbox.
  • Create a file in /documents; in the Drive web UI you should see a new file with an encrypted name. Delete the local file and confirm the encrypted object stays.

The task log (Cloud Sync → Log) records every transfer with direction and result, and it can be exported to CSV from the same tab. From SSH you can watch files arrive:

watch -n 5 'ls -lt /volume1/cloudsync/dropbox | head'

Odd behavior

  • "Cloud Sync failed to connect to Google Drive" or the connection shows "Authentication failed": the OAuth token expired or was revoked (changing the Google password does this). Click the connection → Edit connection → reauthenticate.
  • Files named with characters Dropbox rejects (<>:"|?* on Windows-origin files) show as "Skipped". Rename them locally.
  • The NAS uploads the same file repeatedly: an application on a workstation keeps touching the file. Add an extension filter or move that folder out of the task.
  • Cloud Sync uses a lot of CPU on a small unit during initial sync: it is hashing every file. It settles down after the first pass; you can lower the concurrent file count in the meantime.

Cloud Sync isn't a versioned backup; it's a mirror with a delay. I pair it with Hyper Backup or Btrfs snapshots for point-in-time recovery.