Infrastructure monitoring
Self-hosted alternatives to Datadog, priced
3 open-source tools that can replace Datadog, each shown with what it would actually cost to run for a fleet of 25 servers. Datadog on the Infrastructure Pro tier costs $375 a month at that size.
Start here
Datadog has a free plan for up to 5 hosts, but it keeps metrics for one day only, against 15 months on Pro. That is not a like-for-like replacement for monitoring you rely on, so the comparison uses Pro even at 5 servers.
| Tool | Server only | With your time | vs Datadog | Operational weight | Licence |
|---|---|---|---|---|---|
| Prometheus + Grafana | $12.00 | $124 | +$8,568 | medium | Apache-2.0 |
| Checkmk Community | $26.40 | $139 | +$8,050 | medium | GPL-2.0 |
| Zabbix | $101 | $213 | +$5,371 | medium | AGPL-3.0 |
The final column is the 36-month difference: positive means self-hosting is cheaper.
Which one to pick
Prometheus + Grafana 66,156 stars
Prometheus collects the metrics and Grafana draws the dashboards, with Alertmanager for alerts and node_exporter on each server. Disk follows Prometheus's own capacity formula at its default 15-day retention: about 1,000 series per server scraped every 15 seconds at 2 bytes per sample is roughly 0.2 GB per server. Memory per server is our estimate for the same series count.
At 25 servers it needs 1.6 GB of memory and 15 GB of disk, which fits the Starter 2 GB at VPSServer for $10.00 a month. Setting it up is roughly 6 hours of work, then 1.5 hours a month to keep it healthy. Licence note: Prometheus is Apache-2.0, but Grafana, used here for the dashboards, is AGPL-3.0. That only matters if you modify Grafana and offer it to others over a network.
Full Datadog versus Prometheus + Grafana breakdown · Prometheus + Grafana at every fleet size
Checkmk Community 2,372 stars
The free, open-source edition of Checkmk, with the Nagios core and round-robin metric files that do not grow once created. It installs as one package containing every component it needs. The figures are our estimate: Checkmk does not publish a requirements table we could cite.
At 25 servers it needs 2.6 GB of memory and 11.2 GB of disk, which fits the Starter 4 GB at VPSServer for $22.00 a month. Setting it up is roughly 6 hours of work, then 1.5 hours a month to keep it healthy. Licence note: Checkmk Community is GPL-2.0. Several features, including the faster monitoring core, are only in the paid editions.
Full Datadog versus Checkmk Community breakdown · Checkmk Community at every fleet size
Zabbix 6,394 stars
Zabbix server, a database and the web frontend. Memory is fitted to Zabbix's own hardware table, which asks for 8 GB at 1,000 monitored metrics and 16 GB at 10,000, assuming about 100 metrics per server; beyond 100 servers this runs above Zabbix's own figures. Disk uses Zabbix's database formula at 90 bytes per value, 100 items per server refreshed every minute, 31 days of history and a year of trends: about 0.5 GB per server.
At 25 servers it needs 9.3 GB of memory and 32.5 GB of disk, which fits the Starter 16 GB at VPSServer for $84.00 a month. Setting it up is roughly 6 hours of work, then 1.5 hours a month to keep it healthy. Licence note: Zabbix is AGPL-3.0. That only matters if you modify Zabbix itself and offer it to others over a network.
Full Datadog versus Zabbix breakdown · Zabbix at every fleet size
How the pricing was established
Datadog pricing was read from its own pricing page on 2026-09-21. Server prices come from the providers listed on the hosting page. The sizing model and the cost of your time are set out in full on the methodology page.