Why can't I back up or sync certain files to my cloud storage using HBS?
Last modified date:
2025-08-15
Applicable Products
Hybrid Backup Sync
Details
Different cloud service providers may have different restrictions and limitations on what files can be uploaded to their servers. The following are some common limitations, followed by specific limitations on several popular cloud services listed in alphabetical order.
Common Limitations
- Speed limits are imposed by the cloud storage provider.
- Upload and download file size limitations are imposed by the cloud storage provider.
- File and folder names that do not meet the cloud storage provider’s requirements will be skipped or removed.
- File and folder names ending with a period (.) or space ( ), or that differ only in capitalization may not be supported.
For example, the cloud storage provider may consider “data” and “DATA” to be the same.NoteFor details, see individual sections below for each cloud storage provider, or refer to your provider’s documentation.
- For syncing from the cloud to your QNAP NAS, note that the NAS has character limitations also.Note
- File and folder names ending with a period (.) or space ( ), or that differ only in capitalization may not be supported.
- If you rename a folder during an ongoing RTRR sync job, files within the folder may be removed.Tip
You can use snapshots to mitigate this limitation.
- Only RTRR sync jobs support partial file updates.
For all other types of sync jobs, the entire file is transferred again every time the file is modified, even if the modification is only partial. - Backing up or syncing mounted or external shared folders is not supported.
- For backing up or syncing data on an external storage device connected to your NAS, we recommend using the EXT4 file system on the external storage device for best compatibility.
Box
- To ensure best performance, you can sync up to 100,000 files and up to 100 GB in total size for all files.
- Box recommends syncing only the folders that you are actively working in.
Dropbox
- The names of files and folders cannot exceed 255 characters.
- Dropbox does not allow the characters / \ < > : " | ? * in the path name, and the following files cannot be uploaded to Dropbox:
- System files: desktop.ini, thumbs.db, .ds_store, icon, .dropbox, .dropbox.attr
- Temporary files
- Important
File names beginning with “~$" or " .~”.
- File names beginning with “~” and ending with “.tmp".
- Important
- Files or folders that include trailing spaces.
- Both the Dropbox cloud web console and client app are case-sensitive and do not support having identical file names with different capitalization.
Google Drive
- The size of individual files cannot exceed 5 TB.
- Both the Google Drive web console and Android app supports capital and lowercase file names, but the client app for macOS and iOS does not.
OneDrive
- File names and folder names cannot exceed 256 bytes. The length of the full path must also be less than 430 bytes.
- OneDrive does not allow the characters / \ * < > ? : | in the path name. File names cannot contain leading spaces, trailing spaces, or end with a period (.). Folder names also cannot end with a period (.)
- The size of individual files cannot exceed 10 GB.
- Both OneDrive web console and client app are case-sensitive and do not support having identical file names with different capitalization.
OneDrive for Business
- Folder name and file name combinations cannot exceed 250 characters.
- OneDrive for Business does not allow the invalid characters \ / : * ? " < > | # %. Additionally, a file or folder name that begins with a tilde (~) is not supported.
- The following are illegal file names:
*_files, *_Dateien, *_fichiers, *_bestanden, *_file, *_archivos, *_tiedostot, *_pliki, *_soubory, *_elemei, *_ficheiros, *_arquivo, *_dosyalar, *_datoteke, *_fitxers, *_failid, *_fails, *_bylos, *_fajlovi, *_fitxategiak, *_private - You cannot upload files that have a .tmp or .ds_store extension, and you cannot upload desktop.ini, thumbs.db, or ehthumbs.db files.
- The size of individual files cannot exceed 2 GB.
- You can sync up to 20,000 total items across all synchronized libraries. This includes folders and files.
For the most complete and up-to-date list of restrictions and limitations, please consult your cloud service provider’s official documentation.
Further Reading
For further assistance, ask other users and QNAP experts in the community. Go to QNAP Community
