Server load issues/lag

Velocio: Is the board a LAMP stack app? if yes, have you profiled where most of the load occurs? If you PM me I am happy to have a look at certain aspects of the app for you. Might be able to customize certain aspects.

Also, things that come to my mind when you're talking performance:

• Proper DB indexing
  
• Mysql query caching
  
• Looking into the use of ETags for static files
  
• Looking into etags for cached output that hasn't changed
  
  

Etags don't work with CDN's. And if you examine the site using Firebug you'll see that caching is pretty rock solid.

The DB is indexed thoroughly and correctly. Only slow indexes are the fulltext search. We're using MyISAM for those tables (posts, threads, pms) and InnoDB everywhere else.

MySQL Query cache is enabled, and common queries have been normalised to use a DAL to ensure that the same query can use the cache. We get about 60% hits on those, it does fine.

PHP5 is op-code compiled using XCache.

All common and heavily re-used fragments of data (such as styles, templates, configuration) are stored in XCache.

XCache is running entirely from RAM.

We now have separate DB and Web servers, and the DB server doesn't break a sweat, it's all on the web server, and it's all about Apache2 with XCache (opcode and key/value pairs).

Oh, and I've unloaded all unncessary and unused PHP modules so that only what is needed it loaded by Apache.