I'm glad this thread is not closed and I sure how other jump in.
Assuming that the fundamentals of using updated code, eliminating bad plugins and activating a good caching system, I need to know from the gurus which PHP interpreter works better with WordPress sites on shared hosting.
I've been going back and forth between regular PHP5 (mod_suphp) and PHP5 (FastCGI) (mod_fastcgi) on my bluehost shared hosting account. There are many users/wannabe techs that say that FastCGI is obviously better, but my recent experience says the opposite! For me, the regular PHP is far more stable and better performing than FastCGI. When I had FastCGI running, I would randomly get 10 near-zombie FastCGI processes running for several minutes while visitors were getting 500 errors or garbled pages. The last bluehost tech I talked to on the phone during one of these spikes switch me back to regular PHP and said "WordPress doesn't need FastCGI" (or doesn't work well with it or something similar).
Here are a couple of relevant links for discussion:
Jacob Tirey says here:
SuPHP = Higher CPU but Low Memory Usage
FastCGI = Lower CPU But High Memory Usage
WordPress has an abundance of tiny database queries, multiple file/image loads and PHP is interpreted, so I think that means WordPress is already CPU intensive.
And bjourne says here:
The only problem with fcgi is that it is slightly more complicated and error prone than plain old cgi. For example, if there is a memory leak in the process that serves requests it will cause instability on the server as it slowly eats more and more memory. Memory leaks in cgi won't be noticeable because the processes are restarted all the time. You also need a watch dog process that can restart crashed fcgi processes. Usually, the web server comes with those features builtin, but it is not always the case.
These both indicate to me that FastCGI would be better IF it was configured right.. .right?
So what say you?
I'm in the middle of researching and documenting what works for us (since it is really important to me), so even if no one responds here, I have an article started on allza.info (to be posted later this week).