Heavily used cocoon sites (like the ISE) tend to generate very large cache files ($CATALINA_HOME/work/Catalina/localhost/_/cocoon-files/cache-dir/cocoon-ehcache-1.data) which eventually fill the filesystem and create headaches.

The ISE site is now using a modifed cocoon.xconf ($COCOON_HOME/WEB-INF/cocoon.xconf)to manage this problem. Around line 558 there was a stanza like this:

  <store logger="core.store">
    <parameter name="maxobjects" value="${store.maxobjects}"/>
    <parameter name="use-cache-directory" value="true"/>
  </store>

Which has been changed to this:
  <store logger="core.store">
    <parameter name="maxobjects" value="${store.maxobjects}"/>
    <parameter name="use-cache-directory" value="true"/>
    <parameter name="eternal" value="false"/>
    <parameter name="timeToLiveSeconds" value="0"/>
    <parameter name="timeToIdleSeconds" value="3600"/>
  </store>

So far (in the last 24 hours) the cache seems to behaving and the site isn't crawling, so it looks like we're on the right path.