I have a website on WP... is that at the beginning chose him.
is Apache for nginx also worth eAccellerator posts over 5 000, mostly pictures in the posts is the text.
Plugins — a classic of the genre super cache, Hyper cache and so on trifles.
in the end, around 5 thousand visitors per day drowns dedicated server 2x Xeon 2.8 4 gig of memory.
flushing began when posts exceeded 2.5 thousand, then had to abandon the built-in media Manager, and to organize the images as 1 image in WP is stored in 3 copies + about 300-500 characters for the description of this picture in the DB...
since the extended life of the site, the server breathes more freely, but again, creeping up to 100% loads.
WordPress database highly is not optimal under high load it is not designed, or well designed but the database will require a separate server.