if it's not in ram, you have to do an extra IO to look it up. i don't think you understand how precious metadata space is in a large scale storage system. if you pollute the metadata cache with useless junk like this, you can't cache as many things, your hit rate goes down, and you have to do more IO operations to service each request on average. name one popular distributed file system or object store that compresses everything by default like you are claiming. you won't be able to, because none of them do it, because it's better to leave it to the application.