@hosna Not really sure. What is your Discourse version?
For my configuration, I only upload my discourse backups to another minio s3 server. When I upgraded to 2.3.0.beta6, Admin / Backups started giving an “Internal Server Error” message box. It turned out that it was not actually resolving the bucket-name.backup.example.com domain (DNS-style instead of path-based Bucket naming). It is now working as expected for my minio s3 configuration. 
References:
- Related pull request: #7210, DEV: Remove SiteSetting.s3_force_path_style.
- Related post: S3 migrations from/to minio problems - #41 by rishabh.
- Related minio issue: Support for DNS style S3 Bucket naming.
- Minio Server Config Guide.