Everywhere I worked has been traditional NFS, and I've seen more than 3 times the figure you quoted working well. Usually you have different mountpoints/vfs`s in different servers for different kinds of files.
At rhythm and Hues, you could request footage all the way back from the founding of the studio for example.
CG work is fairly IO intensive for tasks like rendering where you're reading hundreds or even thousands of geometry caches per frame. But for other things, your IO isn't as frequent since it's not about constant r/w as there are long computational or artist time between saves and reads.
Also none of the high end commercial filers are single node - they're all clusters of varying sizes.