Suppose in a peak hour there are 100,000 users that want to watch a video and that on average they consume 10 megabytes per video view. Might be more, might be less. For simplicity, let's say 1 terabyte needs to be served in that hour. That would make a sustained rate of 2222 megabits per second.
The video does not need to be streamed with specific tools, we plan on using some nginx/lighttpd pseudostreaming. Because they are expensive at that rate, we rather do not want to use a CDN.
How many servers do we need (for the network traffic alone), speaking in terms of Xeon quad core servers with 1 gbit/sec connection? What's the maximum on a gigabit connection?
To give you more details: In this peak hour, there are maybe a dozen videos that are accessed. The actual HTML that contains the player etc. is memcached. We already had that much traffic, so that part works. We 'just' need to do it with video now without exploding costs.