Reliable CPU fans

[Richard Fryer]

I have had a fair amount of maintenance on a fairly small cluster (~16nodes)
with Cooler Master fans.

In various workstations I've tried getting Alpha and other brand coolers but
the real reliability issue has been of course the fans.  When specified I've
always chosen a ball bearing (some say 'dual' ball bearing) fans, but this
has not led to spectacular reliability either.

Thermaltake seems to be the best I've used but lacking hours-on data for the
workstations, I doubt the data to be significant.

Has anyone discovered a good resource regarding CPU cooler reliability to
point me to?  Or - taken enough data to have a good opinion?

Thank you
Richard Fryer