I would have responded to this thread earlier but I was out late last 
week.  We had tons of problems with our ldm server running Linux last 
fall which sounds very similar to the behavior you are describing.  I 
had migrated our LDM from Freebsd to Linux (Slackware, not that it makes 
much difference) and had huge problems with I/O waits bogging the entire 
system down. ...
What version of the kernel were you running?  For example
    $ uname -r
    2.6.11-1.14_FC3smp
Versions of the 2.6 kernel earlier than 2.6.10 (I think) appear to have
a very bad I/O performance bug.
I built every release from 2.6.7 though 2.6.9.  I though I had tried a 
release candidate 2.6.10 but it's not in my notes so I'm not sure of the 
details.  I had given up a significant amount of time trying to get it 
to work and had to draw the line somewhere so I migrated back to Freebsd 
at the end of November.  I may revisit Linux on our ldm next time we 
have a hardware upgrade, it just wasn't up to the task at the time.
--
Mark Tucker
Meteorology Dept. Systems Administrator
Lyndon State College
http://apollo.lsc.vsc.edu
mark.tucker@xxxxxxxxxxxxxxx
(802)-626-6328