using nas to keep itunes library on

Windows or Mac OS X?

That will make a difference for specific details. However, generally, in iTunes preferences Advanced pane, you can tell iTunes where to keep your iTunes Media folder. So, if you can create a folder called iTunes Media on the NAS and point iTunes to it, where is says iTunes Media folder location, it should work.

IMPORTANT: Any change you make to the location of the iTunes Media folder is "going forward." Songs added previously will still be stored at the previous location. iTunes does not copy all of your existing media files to the new location because you changed that setting.

To copy your existing media files to the new location, you need to use the command

menu bar -> File -> Library - Organize Library

and use the Consolidate files option. You need to do it this way, instead of manually copying the files to new location (outside of iTunes), because iTunes need to keep track of where all the media files are located. So, when you try to play a song or sync it to an iPod, iTunes knows where to look for the file.

NOTE: You may want try it with a few videos first, to make sure your network connection is fast enough, before transferring your entire iTunes library of media. I prefer a large external drive connected directly to the computer.

Hello, the WD 2TB NAS drives are not that fast. In fact they are on the slow end of their line of drives. They're great for long slow backups, where speed is not very important, such as overnight backups. You are likely to run into speed problems and connection hickups along the way, especially with USB 3.0. It all depends upon your hardware. Most people make the mistake of thinking everything is going to work as advertised, but we know better.

A better solution (but costs more money) is to have a high performance NetGear router, that has a USB 3.0 port on it to connect your external drive. This way all your wired and wireless devices will have access and connectivity 24/7 without worrying about whether your computer is on and connected properly.

I have an Apple TV (3rd Gen) and I watch a lot of iTunes videos and TV shows, so space fills up very quickly even on a terabyte drive. It's not fun when the whole family is watching a HD movie off of Apple TV and the show goes down, when you lose your iTunes folder connection. So, you really have to ensure that you have a quality setup as your iTunes video and music collection grows. The more I think about it, I can see why the Apple iCloud and iMatch concept starts to make more sense for a digital asset management application, because the average user simply is not capable and doesn't want to be constantly thinking like a computer network engineer to keep things working. The idea is for things to work seamlessly without having to worry too much about all the details of every connection.