The 
only constant in this universe is change. Applications, operating systems, hardware, networks, and configurations can and do change on a regular basis.
It’s easy to start the right meters on the wrong system. It’s easy to miss an upgrade or a configuration change. Before any meter-gathering program settles down into its main metering loop, it should gather some basic data about where it is and what else is there. Gather things like:
- System name and network address
- System hardware CPU, memory, disk, etc.
- Operating System release and configuration info
- List of processes running
- Application configuration info
Most of the time this data is ignored, but when weird things happen, or results suddenly stop making sense, this data can be a valuable set of clues as to what changed.
The Every Computer Performance Blog 