choose Data Backup activity:
choose S3 Archive:
choose 'Personalized URL server' and 'signature V4'
Add cs2.cynnyspace.com as server address, and add your access key/ secret key.
List of your bucket will appear - choose anybucket, but an empty one!
Then click next
Choose your source folder:
Or application to backup:
Set multipart upload size to 16 MB (not 512 as default)
Then choose your favorite backup policy, and Apply
Answer yes if you want to backup now:
and backup will start: