Since 1999:<p><a href="http:&#x2F;&#x2F;pmg.csail.mit.edu&#x2F;papers&#x2F;osdi99.pdf" rel="nofollow">http:&#x2F;&#x2F;pmg.csail.mit.edu&#x2F;papers&#x2F;osdi99.pdf</a><p>Google byzantine fault tolerance filesystems to get quite a few more.