How many source ports can be ideally spanned to one destination port? we are planning to use an application in our serverfarm switch but looks like I will have to span more than 20 source ports to one destination, is it doable or recommended way? Is there any Cisco doc that tells us the statistics or utilization for the span ports?
All depends upon the amount of traffic being sent from those 20 source ports. Any exceeded traffic will be dropped without affecting switch performance. This documentation has comprehensive information regarding SPAN on several Catalyst switches