Currently, files you download on BAIDUDL are mostly stored on Amazon S3, but occasionally on Google Drive as well. We use a mix of both to provide the fastest possible download speeds for our users (up to 200 MB/s, depending on your connection).
Google Drive has safeguards in place to protect users from programs and files that may contain potentially unwanted software or malware. However, these measures can occasionally result in false positives. When a file is flagged, we are required to store it on Amazon S3 instead. Fortunately, this typically does not impact performance, as S3 offers comparable download speeds.