Child Item

Synology Cloud Sync is only uploading small files

I have a Synology NAS (DS418Play). I want to use Cloud Sync to back up some folders.

I'm running DSM 7.2.2, Cloud Sync 2.7.2 (Newest).

I have 2 test folders, one encrypted, one clear. The folders contain 2 files. Small.txt (21 bytes) and Big.jpg (3.9 M/b). Small uploads, Big does not.

Synology support checked my config (OK) and found these error in the log:

Curl error: curl(28), http(0), proto(-210), msg(Operation too slow. Less than 1 bytes/sec transferred the last 300 seconds) HandleError: Connection timeout.

What I have tried:

Deleting all folders and tasks and recreating.

Stopping/Starting the service.

Deleting and reinstalling Cloud Sync and database.

Changing the upload bandwidth on the desktop app.

Checked firewall rules and looked for any throttling.

From the desktop app I can sync Gigabyte files, so the problem seems to lie with the Dropbox API.

I know I could set up folders on a PC and copy from the NAS to sync, but that is clumsy and Cloud Sync SHOULD work.

Any suggestions gratefully received.

Find more posts tagged with

Sync

Third Party Integrations

Closed - Partially Delivered

Closed - Inactive

Comments

Jay

Hi @WhiteDwarf500, thanks for messaging the Community!

As this is related to a third party application and integration, the amount of support we can provide is limited.

Have you tried disconnecting the Synology app from your Dropbox account on this page, and then reconnecting it?

Keep me updated with any progress!

WhiteDwarf500

Good though, executed, same result. Small uploads, Big is not.

Jay

Thanks for the info. Have you tried contacting the support team for Synology as to what could be causing this?

I'll leave this post open for other users to comment in with their suggestions.

WhiteDwarf500

Yes, after exhausting the simple fixes, and verifying the connection using Small.txt, they had me send a set of logs. The curl command to the API is timing out:

2026-02-03T14:42:38+00:00 NAS01 syno-cloud-syncd[4104]: [ERROR] upload-download.cpp(262): Curl error: curl(28), http(0), proto(-210), msg(Operation too slow. Less than 1 bytes/sec transferred the last 300 seconds)

2026-02-03T14:42:38+00:00 NAS01 syno-cloud-syncd[4104]: [INFO] worker.cpp(887): Worker (15): HandleError: Connection timeout.

WhiteDwarf500

I have the default amount of storage on Google Drive, so to investigate further, I configured a Cloud Sync connection to Google Drive and picked a small folder to sync. That folder typically contains files > 5 M/bytes. Worked first time. Looks like the problem is either Synology's implementation of the Dropbox API, or my Dropbox configuration.