あとであとで

Subject: Re: Treat disk space like memory space
To: linux-kernel@vger.kernel.org
From: Wes Felter
Date: Thu, 15 Nov 2007 18:03:16 -0600

Stefan Monnier wrote:

> So I'd like to be able to say "these areas of my file-system hold data
> that you can discard whenever you need space". So I can freely fill up
> my disk with such irrelevant data, safe in the knowledge that if I ever
> need this disk space it'll be automatically reclaimed.

James Cipar, Mark D. Corner, Emery D. Berger: TFS: A Transparent File
System for Contributory Storage.

"TFS provides background tasks with large amounts of unreliable
storage-all of the currently available space-without impacting the
performance of ordinary file access operations."

http://www.usenix.org/event/fast07/tech/cipar.html
http://prisms.cs.umass.edu/tcsm/

It's intended for P2P but I could imagine using it for caches.