DOC-3706 RS: Created quorum node documentation

Author: rrelledge

content/operate/rs/clusters/quorum-node.md

@@ -0,0 +1,34 @@
+---
+Title: Set up a quorum node
+alwaysopen: false
+categories:
+- docs
+- operate
+- rs
+description: To reduce infrastucture costs, you can set up a quorum-only node with minimal resources.
+linktitle: Set up a quorum node
+weight: 30
+---
+
+Clusters require an odd number of nodes to maintain [quorum](https://en.wikipedia.org/wiki/Quorum_(distributed_computing)) and avoid [split-brain](https://en.wikipedia.org/wiki/Split-brain_(computing)) scenarios when making decisions. If you need to add another node to a cluster for quorum but want to provision less resources to reduce infrastructure costs, you can set up a quorum node instead of a regular node.
+
+Quorum nodes only participate in voting for cluster quorum decisions and can act as a tiebreaker.
+
+Because quorum nodes do not host database shards or endpoints, they have lower resource requirements. A quorum node should have at least 2 cores and 8 GB of RAM. See [hardware requirements]({{<relref "/operate/rs/installing-upgrading/install/plan-deployment/hardware-requirements">}}) for more details and considerations.
+
+## Enable quorum_only setting
+
+1. Run `rladmin status node` and find a node with no shards:
+
+   ```bash
+   rladmin status node
+   ```
+
+2. Enable `quorum_only` for the node using [`rladmin tune node`]({{<relref "/operate/rs/references/cli-utilities/rladmin/tune#tune-node">}}):
+   ```bash
+   rladmin tune node <quorum-node-id> quorum_only enabled
+   ```
+
+3. Rerun `rladmin status node` to verify. The quorum node will show:
+   - `0/0` shards  
+   - `0KB/0KB` provisional RAM