Generally speaking, we are aware that RadChart has performance problems with large data. That is why in Q3 2011 we introduced our newer charting solution - the RadCartesianChart (part of RadChartView) which was built from the ground up to address this and other deficiencies that we have identified over the years in the RadChart implementation. It is strongly recommended that you use the newer control in such scenarios.
However such severe slow down (10x times) is very unusual. I am not sure what do you mean by "deploy the same application on server". In addition to that there are many other details that may affect the performance, which we will need to check. That is why we will need to know more about your scenario, the way that you have set up the RadChart, etc. It would be best if you could provide a runnable project so we can reproduce the performance issue locally and track-down the problem.
the Telerik team