Question regarding creating comparision graphs

We are in the process of researching to use RRDTool graph to create graphs.

We run load tests periodically. When we run load tests we would collect system metrics like cpu, memory, network etc (using cacti). What we are interested in is to create one graph which will display two data graph lines in the SAME graph PNG file one with one time period for CPU usage and line another time period. So that we can compare if there is any change from test to another.

We run one test on 11/01/2008 from 10AM to 10PM and the next test on 11/03/2008 11AM to 11PM.

Using the RRDTool is it possible to compare cpu usage of both these periods?

Can any one help us out. If it is already in the mailing list please point to the link.

I would greatly appreciate.

Thanks a lot all for the anticipated responses.

Have a great day.

Venkat