Update: We've heard from a knowledgable source that the process described in the Ars story may lead to issues down the road. Specifically, newly purchased or rented video content that ends up on the NAS filesystem may be unplayable due to format errors (previously purchased movies or TV shows should be fine, however).
There's also a vigorous discussion in the Ars forums regarding the wisdom of relocating the library to a case-sensitive filesystem, and suggesting that a symlink to a sparseimage may be a better way to go. Other readers suggested using the $14.99 TuneSpan application to manage the offloading of media to the remote library folder, which would avoid a lot of the complications. If you've got a NAS iTunes library, let us know how you solved these challenges.
Given how many functions iTunes is actually used for these days (iOS syncing, app shopping and buying books, music and movies), it's easier than ever to forget what it was originally used for: listening to music. But of course that's still the software's main function, and if you want to move your entire library over to an NAS -- which stands for network-attached storage, or a hard drive that connects up to a local area network -- then this writeup from Ars Technica has you covered.
The easiest way to share an iTunes library in this way is simply to move the mp3 files (and then re-add them to whatever installation of iTunes you're using), but as Ars says, that will lose all of your collected metadata so far. If you want to actually keep all of your extra data, however, you'll need to actually move your folder location in iTunes to your new NAS folder, and then tell iTunes to copy over all of your collected music and data.
Note that because of the differences between file systems (some may be case-sensitive and some not), just moving your iTunes files location may cause a few issues. And of course having a larger or more complicated library can be problematic as well -- if your library is due for a cleaning, it might be worth it just to say goodbye to the data so far and move on. But iTunes can be resilient if you do your homework before trying to make the move.
There are other ways to do this as well -- you could just share your library from one computer to another with the built-in library sharing feature on your Mac. Or you could move a hard drive around (which might be handy if you need the library in a few different networks, like home and work), keeping your entire library on there. There are plenty of cloud options as well, which will only become more and more easy to use as time goes on.
iTunes may be used for all sorts of other operations these days, but it's still a very robust and powerful music listening and organization app as well.