Join several real filesystems together to form a single larger one

Suppose, you have three hard drives - sized 80, 40 and 60 GB. And 150 GB of music files, which you need to store on these drives. How would you do it?

The two solutions I knew of, were:

  • either to simply have three separate «Music» folders - one per each drive;
  • or create some sort of RAID, joining all the drives into an array.

However, the first method is quite tiresome, as one needs to decide how to split the data between the drives and keep track of what is stored where. For example, I might decide to store all «Classical» music on the first disk, and «Rock» music on the second. Then, suddenly, the first drive fills up and the second one still has plenty of space. Now I need to move the files between the disks, or jump around with symlinks.