docs/Cluster-VictoriaMetrics.md: mention that the -replicationFactor at vmselect is an optional parameter

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Aliaksandr Valialkin 2021-08-25 13:10:24 +03:00
parent c27ee35c5c
commit 9fc9d76a7f

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@ -365,8 +365,8 @@ For example, when `-replicationFactor=3` is passed to `vminsert`, then it replic
so up to 2 `vmstorage` nodes can be lost without data loss. The minimum number of `vmstorage` nodes should be equal to `2*3-1 = 5`, so when 2 `vmstorage` nodes are lost,
the remaining 3 `vmstorage` nodes could provide the `-replicationFactor=3` for newly ingested data.
When the replication is enabled, `-replicationFactor=N` and `-dedup.minScrapeInterval=1ms` command-line flag must be passed to `vmselect` nodes.
The `-replicationFactor=N` improves query performance when up to `N-1` vmstorage nodes respond slowly and/or temporarily unavailable, since `vmselect` doesn't wait for responses from up to `N-1` `vmstorage` nodes. Sometimes `-replicationFactor` at `vmselect` nodes can result in partial responses. See [this issues](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1207) for details.
When the replication is enabled, `-dedup.minScrapeInterval=1ms` command-line flag must be passed to `vmselect` nodes.
Optional `-replicationFactor=N` command-line flag can be passed to `vminsert` for improving query performance when up to `N-1` vmstorage nodes respond slowly and/or temporarily unavailable, since `vmselect` doesn't wait for responses from up to `N-1` `vmstorage` nodes. Sometimes `-replicationFactor` at `vmselect` nodes can result in partial responses. See [this issues](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1207) for details.
The `-dedup.minScrapeInterval=1ms` de-duplicates replicated data during queries. If duplicate data is pushed to VictoriaMetrics from identically configured [vmagent](https://docs.victoriametrics.com/vmagent.html) instances or Prometheus instances, then the `-dedup.minScrapeInterval` must be set to bigger values according to [deduplication docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#deduplication).
Note that [replication doesn't save from disaster](https://medium.com/@valyala/speeding-up-backups-for-big-time-series-databases-533c1a927883),