Hi,
The average bitrate assuming all streams are played with an equal number of clients is 2.8 Mbps per client.
We see loss of around 20% from NICs, (1 Gbps gets you around 800 Mbps) so 4 Gbps should get you around 3.2 Gbps which is 1,140 connections.
Depending on how many clients are watching live and how many are watching from the nDVR window (not live) you may be limited by the speed of the disks.
A standard 7200 RPM disk gets around 80 clients playing VOD content. I see you have multiple disks which will increase this number.
A good guide would be to request load testing tool and see how many connections the server can handle for a live stream (at 2.8 Mbps) and another test for VOD content.
Our load testing tool only supports RTMP so you can’t test the nDVR stream but can get an idea on the limitations of disk and bandwidth which are the usual bottlenecks.
How to get Flash RTMP Load Test Tool
Regards,
Jason