# Replace a Running Node in a Scylla Cluster¶

There are two methods to replace a running node in a Scylla cluster

## Add a new node to the cluster and then decommission the old node¶

Adding a new node and only then decommissioning the second node allows the cluster to keep the same level of data replication throughout the process, but with a cost. When adding a new node to a Scylla cluster, existing nodes will give the new node responsibility for a subset of their vNodes, making sure that data is once again equally distributed. In the process, these nodes will stream relevant data to the new node. When decommissioning a node from a Scylla cluster, it will give its vNodes to others nodes, making sure data is once again equally distributed. In the process, this node will stream its data to the other nodes. Hance, replacing a node by adding and decommissioning redistribute the vNodes twice, streaming a node worth of data each time

### Procedure¶

1. Follow the Adding a New Node Into an Existing Scylla Cluster procedure
2. Decommission the old node using the Remove a Node from a Scylla Cluster procedure
3. Run the nodetool cleanup command on all the remaining nodes in the cluster
4. Verify that the node removed using nodetool status command

## Replace a running node - by taking it place in the cluster¶

Stopping a node and taking its place in the cluster is not as safe, as data replication is reduced during the process. However, it is more efficient, as vNode distribution does not change, and only one node worth of data is streamed

### Procedure¶

1. Run nodetool drain command (Scylla stops listening to its connections from the client and other nodes).
2. Stop the Scylla node you want to replace
sudo systemctl stop scylla-server

sudo service scylla-server stop

docker exec -it some-scylla supervisorctl stop scylla


(without stopping some-scylla container)

1. Follow the Replace a Dead Node in a Scylla Cluster procedure
2. Verify that the node is successfully replaced using nodetool status command