Reconnoiter is described as 'monitoring and trend analysis system designed to cope with large architectures (thousands of machines and hundreds of thousands of metrics)'. There are seven alternatives to Reconnoiter for a variety of platforms, including Linux, Online / Web-based, Self-Hosted solutions, Python and fontconfig. The best alternative is Graphite, which is both free and Open Source. Other great apps like Reconnoiter are RRDTool (Free, Open Source), OpenTSDB (Free, Open Source), Axibase Time Series Database (Free) and Cube (Free, Open Source).
RRDtool (acronym for round-robin database tool) aims to handle time-series data like network bandwidth, temperatures, CPU load, etc. The data are stored in a round-robin database (circular buffer), thus the system storage footprint remains constant over time.
ATSD is purpose-built for analyzing and reporting on massive volumes of time-series data collected at high frequency. Features include data analytics, visualization, data forecasting, reporting, alerting. All in one product built for big data.
Cube is a system for collecting timestamped events and deriving metrics. By collecting events rather than metrics, Cube lets you compute aggregate statistics post hoc. It also enables richer analysis, such as quantiles and histograms of arbitrary event sets.