[CentOS] Centos 4.3/ 64-bit: Java/ Tomcat Optimization

Hi,

I have been steadily migrating machines, about 50-70 of them to Centos
4.3, mostly using Opteron Dual Core/ Tyan boxes of Supermicro origin.

They perform apache, mysql, tomcat and qmail work, depending where they exist

The main reason from the programmer side (i'm a sysadmin/ engineer) is the
larger "heap size" to satisfy some of the needs.  Since Java/Tomcat
applications can also be I/O intensive, i'm looking at things from the
systems side to improve on, kernel settings, filesystem choice, RAID
configuration, etc.

Is there anyone out there in the Centos 4.3 community that's looking at
similar optimation interests, and if so, what have you found thus far? 
Mostly i'm curious about stability, features, bugs and other aspects
native to Centos 64-bit/4.3 and running Tomcat/ Java on it.  Right now we
are at Java 1.4, but will likely make the jump to 1.5 within the next 180
days.

So far the developers are happy with the first box I made for them, but I
did not customize the kernel, or make any in-depth adjustments, just
handed them a larger heap size and they seemed quite happy with that in
itself.

Clustering, keeping alot of single machines separate, getting one large
machine with alot of mem/cpu/i/o capacity, these are all being examined. 
Just curious what you think, or if you know of any great resources on the
subject.

I'm in a similar boat wih regard to Mysql, but that's another story, and I
have alot of actual research on that to share.

-karlski