Hi @yasser Mohamed AbdelMoneim ,
1.If your file server is a NAS-like hardware shared server instead of local file storage, the official documentation does not indicate whether it is supported. If the file server can be migrated in the form of a local file share, it is recommended that you try the official migration tool (Microsoft SharePoint Migration Tool). If you are using a file server that cannot be migrated as a local file share, you could try using a third-party tool to migrate.
Migration forms like this:
2.Regarding file permission changes during migration, for users that have been mapped between on-premises and SharePoint, all unique permissions on files will be migrated to SPO, but inherited permissions will not be migrated. Files without user mappings will be assigned the default permission of the location to which it has been migrated in SPO.
Reference: File and folder permissions when using the SharePoint Migration Tool
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