First, you must be running nightlies to be able to use two physical disks. You will run into strange problems using two disks with 0.2.4, including songs missing from the database.
If you are running nightlies, then you can do something like this:
user@slug:~$ mkdir /share/flash/data/public/mp3
user@slug:~$ cd /share/hdd/data/public/mp3
user@slug:/share/hdd/data/public/mp3$ ln -s /share/flash/data/public/mp3 otherdisk
Then the contents of the “otherdisk” directory will be the stuff in /share/flash/data/public/mp3.
Remember, you have to be using nightlies to do this though.
The next nightlies drop will have support for multiple mp3_dir entries, though, so when the next nightlies come out (svn-980 or so), then you’ll be able to put both directories in there.
— Ron