CentOS - Jun 2006 - 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

> 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.
Most of the tuning I've done so far has been filesystem related, and
application specific with respect to recommendations for tunables in
/etc/sysctl.conf, but I'd be very interested to hear about what you've
got for mysql tuning. Anything you'd be willing to share with the
community I'm sure would be warmly welcomed.

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Java eh? I guess that means memory hog?

Mostly Opterons you say...so...what are the none Opterons running? Have 
you noticed swapping on non-Opteron boxes?

Opterons have automatic memory handling advantages without tuning under 
the Linux kernel.


As for I/O, it depends on what kind of patterns you have and what kind 
of behaviour do you require. Do you have lots of files in a single 
directory? Do you require sync? What is your RAID for?

I have had plenty experience in squeezing performance out of 2.6 kernels 
but not that much with Centos 4.x boxes except for discovering that 
Centos 4.x kernels don't cut it. As to why I found out later but that 
only applies to Intel-based processors apparently...that is the bad vm 
patch Redhat applied to their kernels of which the removal will come in 
Update 4.


RHEL 4 limiting themselves to ext3 leads to there being less to try...

Anyway, I am very into optimization since that was how I did not have 
ask for extra machines for the mail server clusters that I use to watch 
over in my previous job.