docs/FAQ.md: add a question about the difference between vmagent and Prometheus

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Aliaksandr Valialkin 2020-06-03 20:56:22 +03:00
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@ -20,6 +20,29 @@ See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/
See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/wiki/Quick-Start).
### What is the difference between vmagent and Prometheus?
While both [vmagent](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md) and Prometheus may scrape Prometheus targets (aka `/metrics` pages)
according to the provided Prometheus-compatible [scrape configs](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config)
and send data to multiple remote storage systems, vmagent has the following additional features:
- vmagent usually requires lower amounts of CPU, RAM and disk IO comparing to Prometheus when scraping big number of targets (more than 1000)
or targets with big number of exposed metrics.
- vmagent provides independent disk-backed buffers per each configured remote storage (aka `-remoteWrite.url`). This means that slow or temporarily unavailable storage
doesn't prevent from sending data to healthy storage in parallel. Prometheus uses a single shared buffer for all the configured remote storage systems (aka `remote_write->url`)
with the hardcoded retention of 2 hours.
- vmagent may accept, relabel and filter data obtained via multiple data ingestion protocols additionally to data scraped from Prometheus targets.
I.e. it supports both `pull` and `push` protocols for data ingestion.
See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#features) for details.
- vmagent may be used in different use cases:
- [IoT and edge monitoring](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#iot-and-edge-monitoring)
- [Drop-in replacement for Prometheus](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#drop-in-replacement-for-prometheus)
- [Replication and High Availability](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#replication-and-high-availability)
- [Relabeling and Filtering](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#relabeling-and-filtering)
- [Splitting data streams among multiple systems](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#splitting-data-streams-among-multiple-systems)
- [Prometheus remote_write proxy](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmagent/README.md#prometheus-remote_write-proxy)
### Is it safe to enable [remote write](https://prometheus.io/docs/operating/integrations/#remote-endpoints-and-storage) in Prometheus?
Yes. Prometheus continues writing data to local storage after enabling remote write, so all the existing local storage data