Let me just say my experience with persistant connections did not work out. I have two Threads systems on my dual xeon processor dell server with 2gb of ram. I fugred persistant would be good. I was very wrong.

SHOW STATUS showed hundreds of connections, many waiting on a timeout. 100% memory usage and about 1.5gb of swap usage. My server went from 2,000 queries/min to its current level of around 6,000 queries/min and persistant connections was a real bad idea.

Just in case anyone else was considering it - it would seem that high traffic sites should avoid this.

I'd like to see an explanation of exactly how a persistent connection works, as opposed to a non-persistent connection.

1) What processing is performed when creating/destroying a non-persistent connection?

2) What processing is performed when re-using a persistent connection?

3) How much resources (memory, disk space, etc.) does a "connection" take?

4) When using persistent connections, is there any risk of users getting data intended for a different user?

There's a chapter in the php manual, that explains the basics:

http://www.php.net/manual/en/features.persistent-connections.php

Is this Persistant option you refer to the one within UBBT config or in my.cnf file?

UBBT.... I will say that the persistant feature *may* be benefitial on smaller sites; its just that I run a Dual Xeon processor machine with 2GB of RAM and the hundreds of processes running killed my server.