John Chambers wrote....
...The basic problem I'm looking at is that the machine will be chugging
along, happily running a bunch of processes. Then suddenly they all
slow to a crawl, something like 10 to 100 times slower. There are
delays of a minute or more in things like writing a tiny file..... 


redhat.com/support/wpapers/redhat/ext3/
try the data=writeback option
also, sgi.com has a great open source journaling filesystem as an alternative to ext3, I run it now on RH8.
Do you use google.com to find info?