Good start panthro,

You could salt the hash in a couple of ways:

1. Like how Aranxo is surmising, add the date_created to the filename and then the hash after, maybe with or without some delineator.
2. Keep the filename, create some sort of hash (MD5, sha256, etc), and then truncate the hash to a length where it and the filename are constant across all records.

Point two could be more interesting, since it would stop the collision case in Aranxo's answer where two MD5 hashes collide at the same time, making the timestamps equal (down to the lowest integer) and the MD5 hashes equal.

HPC might see this use case for large(n) file storage requests.

Also, point two would implicitly enforce a character limit on the filename length, which could prevent malicious or accidental failures on the system.

Salting the hash more, with perhaps additional metadata like IP where the request was made, or even the username if the user agrees to this in a Privacy Policy.