Ronald G. Minnich, "The AutoCacher: A File Cache Which Operates at the NFS Level", USENIX Technical Conference Proceedings, pp. 77-83, Winter 1993, San Diego, CA.
Minnich extended an old version of Amd to do something similar. The paper is too old to be on Usenix's online library, but Erez Zadok has those proceedings in his office.
Consider the Usenix '92 paper "Discovery and Hot Replacement of Replicated Read-Only File Systems, with Application to Mobile Computing", from http://www.cs.columbia.edu/~ezk/research/. In that work, Erez Zadok describes failover from one dead NFS to another working one.