I am sorry - I think I put the previous comment in the wrong place. The comment interface is a bit confusing, or maybe I am just confused.

I also missed the clustering discussion - looks like you are already doing a lot of that.

But still, I do recommend Varnish and putting some pressure off Apache. It will save quite a few CPU cycles.

Also, I just discovered that plos.org does not compress content! This must be the reason the site appeared 'slow' to me. Look:


[toyvo@asusie ~]$ HEAD -H "Accept-encoding: gzip, deflate" http://www.plos.org/cms/node/334
200 OK
Connection: close
Date: Tue, 18 Mar 2008 00:15:21 GMT
Server: Apache/2.0.52 (CentOS)
Content-Type: text/html; charset=utf-8
Client-Date: Tue, 18 Mar 2008 00:04:59 GMT
Client-Peer: 209.237.233.125:80
Client-Response-Num: 1
Set-Cookie: PHPSESSID=************************; expires=Thu, 10-Apr-2008 03:48:41 GMT; path=/
X-Powered-By: PHP/4.3.9


Please do enable that. For large pages, it reduces the load time considerably. It is not that difficult to install, just use
mod_deflate.

Thank you for the good work with PLoS.

Kind regards,

--Anton