someone can help me to explain why from server-status on an IBM HTTP-Server I got 0,5 MB/second and from Introscope I see about 40M on 15 sec interval (also the invocations number are different) ?
Generally when using an outside source to monitor metrics, they will not align with Introscope. The reason for that is from an excerpt here.
Metric Requirements and Recommendations - CA Application Performance Management - 10.0 - CA Technologies Documentation
Most agents report metrics to the Enterprise Manager at 7.5-second intervals. The Enterprise Manager processes metric data at 15-second intervals called time slices. The processing of time slices is named the harvest cycle. During the harvest cycle, the Enterprise Manager aggregates the two sets of metrics data that the agents reported. This aggregated data is processed to perform calculations, check alerts, update heuristics, and update Workstation views. Raw (agent-based) and processed metrics are persisted to the SmartStor database.
I hope Matt's answer was helpful. Please let us know if that is the case. Since it addressed the situation, I am am marking as answered. You may ask additional questions as needed.