XFileSharing Pro - When to add a new fileserver?

[Ryok]

I want to ask when to add a new fileserver. I already have 5000 videos stored on my main server. And 200-300 people are streaming the videos at the same time. The speed still looks okay for me.
my server is 2x Intel Xeon 5620 and currently consuming 30% of my disk space ..
what are the factors that i need to know when to add a new server.

sorry for my bad english/

[natar]

Did you already Run db to file consistency check, run file to db consistency check and run update serves file used?