Originally Posted by silvyus_06
I read somewhere that having a lot of small partitions is useful to speed .
That's true for FAT format partitions as the way they do directory structures and free-space calculation doesn't scale all that well. More modern filesystems don't have this problem though.
The main advantage of multiple partitions is that if one is unlucky enough to encounter filesytem structure corruption, it doesn't take the other one with it. They're also faster to fsck in the event of that being necessary.
From what little Dave has said in his initial post, I'd be inclined to have one partition for the music and one for the backups.
Filesystem type depends on where the disk is going to be used. Personally, I'd stick with either ext4 or ntfs (if you intend to use it on Windows). I'm not sure the more exotic filesystems are worth the effort. I used to use JFS myself, but sadly that one seems to be falling by the wayside and some distros don't even include support for it any more.