I think you will gain more if you use the latest version of PHP and
latest version of MySQL 5.1 to get the best performance out of your
default settings.
Good Lord man, am I seeing those numbers correctly?
For one thing, vBulletin is resource-hungry. I personally would go with
phpBB3. I’ve had a few hundred people logged into phpBB3 and my memory
usage hasn’t gone above 400MB, with Apache <— yes apache, and MySQL
together.
Also, take a look at optimizing you MySQL config, there is not much
you can do about the php.
Upgrade your PHP and MySQL as per my previous email. let MySQL run for
at least 48 hours and run this on the server
To do so will drop security serveries from debian, then you must take
care
all the security patches by yourself then. The latest versions tend to
come
with new bugs also and can’t always give best performance most of time.
Just compile php-fpm together with patches and source from debian/lenny
with
php-5.26, then recompile it when debian updates php for security, thus
you
needn’t to worry about security things.
What you are talking about is not as valid for PHP and MySQL for
example where these distributes tend to be always one major version
behind. Zend Server ships with the latest PHP 5.2.9 and their pretty
much sell it to their enterprize customers. MySQL 5.1 has seen good
improvements and is currently well into stable state.
I would not use bleeding edge version of OS software but the web
development stack updates pretty often with needed updates.
Seconded, I would bet that your mysql instance is doing a lot of IO,
mainly because your innodb buffer size is set to low. Given your
sharing that machine with a bunch of php processes you’ll have to
tread carefully to avoid swapping.
I would enable the slow query log (don’t forget to set the reporting
interval to 1 second, the default is 10) and also log queries that
don’t use indexes. Some schema tweaking may be in order.