NFS caching issues on 2.4

[Phil Oester]

I've stumbled upon a wierd NFS caching issue on 2.4 which does not seem to
exist in 2.2.  Our www docroot is NFS mounted on a NetApp 760.  We have a
cron job which make changes to the index.html every 5 minutes.

Recently, we upgraded all the web servers to 2.4 and noticed that there were
big delays in seeing these 5 minute updates.  Yet, an ls -l in the nfs
directory on each of the servers clearly shows the new timestamp.  However,
a cat of the file shows that it is the old version (sometimes up to 1 hour
old).  I was using NFSv3, so decided to try NFSv2, but got the same results.

I reverted to 2.2.19 on the boxes (which are RedHat 7.1 incidentally), and
these problems went away.

Any ideas why this is happening?

-Phil Oester