i see the server is sometime very slow.

do you use PHP cache software like eaccelerator ? it can brings spectacular performance enhancement on PHP pages.

http://eaccelerator.net/

i use this software at my work on production servers for intranet/internet and it definitively helps.

here is some thread about the use of eaccelerator with vbulletin
http://www.vbulletin.com/forum/showthread.php?t=75878

Hi...

Yes, all 4 of our AVS web servers run it. (Even the ad server and the archive servers.)

They are all hitting one MySQL server however which sometimes makes for the issue. But not to worry, a new Dual Quad Processor server with 8 Gigs ram is currently being built for use as the MySQL server.

Hi...

Yes, all 4 of our AVS web servers run it. (Even the ad server and the archive servers.)

They are all hitting one MySQL server however which sometimes makes for the issue. But not to worry, a new Dual Quad Processor server with 8 Gigs ram is currently being built for use as the MySQL server.

mysql
Thats your problem ;)