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Knowledge Center

Supported File Attributes of Each Cloud

To ensure your files and folders sync correctly, please note the following information.

PlatformFile hashLast modified time
Synology C2 Object StorageO (md5)X
Alibaba Cloud OSSO (md5)X
S3 StorageO (md5)X
Backblaze B2O (sha1)O1
BaiduO (md5)9X
BoxO (sha1)O
DropboxXO
Dropbox Team SpaceXO
Google Cloud StorageO (md5)O1
Google DriveO (md5)O
Google Shared DriveO (md5)O
hicloud S3O (md5)X
HiDriveXX
JD Cloud OSSO (md5)X
MegaFon MegaDiskO (md5)O
Azure StorageO (md5)9O1
Microsoft OneDriveO (sha1)O
Microsoft OneDrive for BusinessXX
Microsoft SharePoint OnlineO (QuickXOR)X
OpenStack SwiftO (md5)O1
Tencent Cloud COSO (md5)X
WebDAVXX
YandexXX

Note:

  1. These public cloud providers do not allow the last modified time attribute to be updated, but provides a custom file attribute field for third-party apps like Cloud Sync. Cloud Sync will save the last modified time in the customized file attribute field. This means Cloud Sync's last modified time will not be updated on the public cloud web interface and other sync clients.
  2. Due to the file system limitation, after you modified the data on your Synology NAS, the last modified time of the directory on your cloud service and Synology NAS may be different.
  3. Only Box, Dropbox, Google Drive, MegaFon MegaDisk, and OneDrive allow third parties to update the last modified time, meaning that the last modified time of other public cloud services is always the time when files are uploaded.
  4. Hash values are not available for files uploaded to S3 Storage, Alibaba Cloud OSS, Tencent Cloud COS, or JD Cloud OSS via multi-part upload.
  5. Hash values are not available for files uploaded to OpenStack Swift via Dynamic Large Object upload.
  6. Hash values are not available for files uploaded to Backblaze B2 via b2_upload_part upload.
  7. Cloud Sync uses Google Cloud Storage's md5 hash. The crc32 hash of composite object is not adopted.
  8. Increasing the number of concurrent uploads/downloads can improve synchronization performance when the network and resource conditions allow.
  9. After files have been uploaded to Baidu Cloud/Azure Storage, Cloud Sync will compare the file hash on both sides to confirm consistency. We found that in many cases, Baidu/Azure Storage will respond with an incorrect hash value, causing Cloud Sync to detect that the files on the public cloud differ from those on your Synology NAS. Because of this, Cloud Sync will try to align the versions, and commence sync again, causing the repeated download of the same file.