multiple databases

I'd like to run this past anyone who'd care to comment before I get too far down the track I'm considering taking with a PHP web portal site. Is it a wise idea to have a PHP web application running on multiple databases? Everything I've done to date has run off one database, no matter how large it got. With the current small portal site, the idea is to break a monolithic database up into around 10 smaller databases, each of which should be able to be backed up to a floppy. Not all databases are called on each page, but up to 6 or so could be. What are the performance implications (slower, obviously, but 10 times slower?). Performance beyond what the human mind can perceive is not relevant to me. Should I use mysql_connect or mysql_pconnect for each db connection ? Should I be careful to use mysql_close with each connection? Any advice appreciated. Mick