No server response code on insert: how do I avoid this at high speed?

[Paleo Tek]

I have a largish index with a lot of churn, and inserts that come in 
large bursts.  My server is a multiprocessor with plenty of memory, so I 
can multi-thread and stuff in about 1.6 million records per hour, going 
full speed.  I use a dozen or so threads to post curl inserts, and 
monitor the responses.

Using jetty, there is ~10% failure rate with no server response code 
received.  Switching to tomcat reduces the error rate to around 2%.  
(which makes me like tomcat  a lot, even though I'm a dog person...).  I 
suspect I'm overrunning the capacity of the servlet container.  Tweaking 
parameters in Jetty improved performance, and I can tune Tomcat.  But 
then I'll just be overrunning a tuned system, at a slightly faster rate.

My work around is to keep track of which inserts fail, but I suspect 
there's a better approach.  Any suggestions how I can balance maximum 
insert speed with a low error rate?  Thanks!

         -Jim