For all my new PHP work I have been using SQLite as the database since it's reasonably fast for small sites and can be backed up by moving a single file.
SQLite however does not terribly like being on an NFS mounted volume (which at my ISP is the only choice). Every time they reboot the server (which doesn't happen often) all my SQLite database files suddenly lock up the process reading them; this can only be cleared by the ISP rebooting the (shared) server a second time. It's funny that even creating a new empty SQLite database and trying to open it with the command line tool exhibits the same issue. I think it must be some temporarily file that was locked and is not in a clearable state due to the reboot.
Sigh, so trying to save a bit of effort doesn't pay off; I'm now switching to MySQL for everything and doing the usual update sql scripts. Oddly enough the performance is less since the database connection time has increased (the database is on a different server).