Slow server

[Olivier Nicole]

Hi,

I am trying to deal with a server that is getting slower and slower.

Machine is based on a AMD Opteron(tm) Processor 244 with 4GB memory.

It is running MySQL, and Apache 13 and serving about 400 web sites
written in PHP.

OK the design of PHP is certainly not the most efficient, but actually
the server cannot hold 50 simultaneous http connections.

I am wondering:

1) what optimization I should look for in the system

2) as there are many connections comming from search engines siders
   (90% of all the established connections), I'd like to limit the
   ressources that spiders are using. One way would be through IPFW,
   but are there better ways? Is there a way to limit/prioritize in
   Apache (not that I know any).

Best regards,

Olivier