Opendcim - a free, web based Data Center Infrastructure Management application.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
NetZoom - Use NetZoom Data Center Infrastructure Management (DCIM) Solutions to solve data center challenges of managing Assets, Change, Capacity, Connectivity while Optimizing Power, Space, and Cooling.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Symantec Server Management Suite - Symantec Server Management Suite provides solutions to provision, control, automate, and monitor physical and virtual servers across a wide array of platforms.
Prometheus - An open-source systems monitoring and alerting toolkit.