Monit!

Munin is a networked resource monitoring tool that can help analyze resource trends and "what just happened to kill our performance?" problems. It is designed to be very plug and play. A default installation provides a lot of graphs with almost no work.

Datadog is a monitoring service for IT, Dev & Ops teams who write and run applications at scale, and want to turn the massive amounts of data produced by their apps, tools and services into a unified view of IT infrastructure. Datadog's capabilities are provided on a SaaS-based data analytics platform that enables multiple teams to work collaboratively on infrastructure issues.

netdata is a system for distributed real-time performance and health monitoring. It provides unparalleled insights, in real-time, of everything happening on the system it runs (including applications such as web and database servers), using modern interactive web dashboards.

Cabot is a free, open-source, self-hosted infrastructure monitoring platform that provides some of the best features of PagerDuty, Server Density, Pingdom and Nagios without their cost and complexity.

Check_MK is comprehensive IT monitoring solution in the tradition of Nagios. Check_MK is available as Raw Edition, which is 100% pure open source, and as Enterprise Edition with a lot of additional features and professional support.

Cacti is a complete frontend to RRDTool, it stores all of the necessary information to create graphs and populate them with data in a MySQL database. The frontend is completely PHP driven. Along with being able to maintain graphs, data sources, and Round Robin archives in a database, cacti handles the data gathering. There is also SNMP support for those used to creating traffic graphs with MRTG.

Axibase Time-Series Database (ATSD) is a next-generation statistics database. ATSD is for companies that need to extract value from large amounts of time-series data which exists in their IT and operational infrastructure. Built on top of Hadoop Distributed File System (HDFS), ATSD delivers scalability and performance beyond relational database limitations.

Zenoss (Zenoss Core) is an open source application, server and network management platform based on the Zope application server. Released under the GNU General Public License (GPL) version 2, Zenoss Core provides a web interface that allows system administrators to monitor availability, inventory/configuration, performance and events.

Monitorix is a system monitoring tool designed to monitor as many services and system resources as possible. Due to its simplicity and small size it can also be used on embedded devices.

GFI MAX RemoteManagement allows IT Support Companies & Service Providers to manage customer's IT devices from Desktop, Tablet & Mobile.

NetXMS is an enterprise grade multi-platform open source network management and monitoring system. It provides comprehensive event management, performance monitoring, alerting, reporting and graphing for all layers of IT infrastructure — from network devices to business application layer.

Our open and flexible server and network monitoring solution delivers a unified view of your entire IT environment. Monitor up to 100,000 devices from a single server, with distributed and redundant solutions for nearly infinite scalability.

LiveMon is a cloud-based monitoring software designed for IT teams, Dev-ops, CIOs, and Infrastructure & Application Directors. The Artificial Intelligence detects incoming IT performance incidents before they actually harm your business services. You prevent fires rather than fighting them. With unlimited scalability, you can monitor all types of environments from one server to over 100,000 severs with heterogeneous application sets to get a unified view of all the interactions, performance KPIs and data patterns. LiveMon will help you detect and solve any anomalies, optimize your infrastructure utilization, and correlate events. Packaging server monitoring and web-performance monitoring along with log analysis and storage, LiveMon is the only SaaS solution that gives you real-time 360° end-to-end visibility of your Information System. Thanks to LiveMon you no longer have to waste valuable time digging into your IT to find the right information, everything is visible in a single glance. »