One of the tools we often use for monitoring and measuring the performance OTM systems is sar, though unfortunately graphing and analyzing the resultant files can be a pain in the ***. For our internal systems, we've configured a web application, based on Nagios and Cricket (like MRTG) to monitor both current and historical performance trends.

However, when working on-site, this framework isn't available and we rely on a Java application called kSar. We're found this utility useful, both in the analysis phase and for creating graphs for use in presentations and reports. To help get you started, I've attached some links that introduce kSar, how it's used and sar in general.

kSar:sar:Hope this helps!