Performance monitoring rarely evokes the gut-wrenching debates or religious commentary that other topics do, but it's a very important part of the system administrator's job. System performance is an essential, but often neglected, metric, even in our new disposable hardware world.
For many admins, performance monitoring consists of listening to user complaints about slowness, sluggishness, or some equally subjective description. Sometimes the descriptions don't help much at all. What you really want to know is, what is causing the sluggishness?
Today, we have better tools than just our intuition and opinions. We also have more systems, virtual and physical, than we can effectively manage psychically. You need software tools that measure system, network, and application performance in an objective way. You need real data with which to make decisions. In the "old" days, if a system had performance problems, we added more RAM. If a disk filled to near capacity, we replaced it with a larger one. If the network was slow, we rebooted something.
To make the case for lowering costs via performance monitoring, you have to be creative and select the software that makes economic sense for your company. The information you'll need to gather falls into three categories: historical data, performance trends, and capacity projections. You'll need all three for a complete picture of performance. Be aware, however, that your specific circumstances might dictate that you use a variety of tools to achieve your goals. Don't allow the use of multiple products to deter you from exploring free software alternatives.
Open source software (OSS) has thankfully replaced the old and outdated business adage, "You have to spend money to make money." You can do a lot with free software – and you should. OSS has advantages other than price alone. Open source tools are more likely to run on older or decommissioned hardware, and you will have access to the source code for those tweaks, enhancements, and customizations you don't enjoy with most commercial products.
Performance monitoring is necessary, but not a necessary evil. It saves you money by preventing unneeded hardware purchases and upgrades. It can keep your system administrators informed about any problems on a data center--wide basis. Additionally, if you select your software from the open source software bucket, you'll prevent performance problems in your bank account.
Quality performance tools will give you the objective data, graphs, and reports that show historical performance trends and projections that you'll need to make informed capacity decisions. No intuition or psychic ability required.