The data center is a complicated organism. In order to get the most out of your data center you need to keep it healthy, and just like keeping yourself healthy, you'll need to monitor your data center constantly. Here are a few piece of data you should be monitoring to keep your data center in tip-top shape:
Power trends can save you time and money by showing you what your data is capable today and how to expand to prepare for the future. Ideally you should be able to overlay different time periods (such as this month with last month) or overlay different metrics such as power and temperature for advanced analysis (to understand at the current growth rate when a power or environmental threshold will be exceeded at the current growth rate).
Temp and Humidity
Ever increasing densities of vertically racked servers conserve valuable floor space in the data center, but the resulting power consumption and heat dissipation create new concerns for data center managers. Environmental Monitoring, particularly temperature & humidity, is a must for any sensitive infrastructure. Monitoring temperature in equipment cabinets is vital to the server's performance and controlling infrastructure cooling costs.