Administration Guide

For training material, also check out the Admin Procedures lesson on Scylla University.

System requirements

Make sure you have met the System Requirements before you install and configure Scylla.

Download and Install

See the getting started page for info on installing Scylla on your platform.

System configuration

See System Configuration Guide for details on optimum OS settings for Scylla. (These settings are performed automatically in the Scylla packages, Docker containers, and Amazon AMIs.)

Scylla Configuration

Scylla configuration files are:

Installed location


/etc/default/scylla-server (Ubuntu/Debian) /etc/sysconfig/scylla-server (others)

Server startup options


Main Scylla configuration file


Rack & dc configuration file

Address Configuration in Scylla

The following addresses can be configured in scylla.yaml:

Address Type



Address Scylla listens for connections from other nodes. See storage_port and ssl_storage_ports.


Address on which Scylla is going to expect Thrift and CQL client connections. See rpc_port, native_transport_port and native_transport_port_ssl in the Networking parameters.


Address that is broadcasted to tell other Scylla nodes to connect to. Related to listen_address above.


Address that is broadcasted to tell the clients to connect to. Related to rpc_address.


These are broadcast_addresses of seeder nodes.


Node’s address resolution helper.


Address for REST API requests. See api_port in the Networking parameters.


Address for Prometheus queries. See prometheus_port in the Networking parameters and Scylla Monitoring for more details.


Address of the node this Scylla instance is meant to replace. Refer to Replace a Dead Node in a Scylla Cluster for more details.


When the listen_address, rpc_address, broadcast_address, and broadcast_rpc_address parameters are not set correctly, Scylla does not work as expected.


The scylla-server file contains configuration related to starting up the Scylla server.


scylla.yaml is equivalent to the Apache Cassandra cassandra.yaml configuration file and it is compatible with relevant parameters. Below is a subset of scylla.yaml with parameters you are likely to update. For a full list of parameters, look at the file itself.

# The name of the cluster. This is mainly used to prevent machines in
# one logical cluster from joining another.
cluster_name: 'Test Cluster'

# This defines the number of tokens randomly assigned to this node on the ring
# The more tokens, relative to other nodes, the larger the proportion of data
# that this node will store. You probably want all nodes to have the same number
# of tokens assuming they have equal hardware capability.
# If you already have a cluster with one token per node, and wish to migrate to
# multiple tokens per node, see
num_tokens: 256

# Directory where Scylla should store data on disk.
    - /var/lib/scylla/data

# commit log.  when running on magnetic HDD, this should be a
# separate spindle than the data directories.
commitlog_directory: /var/lib/scylla/commitlog

# seed_provider class_name is saved for future use.
# seeds address are mandatory!
    # Addresses of hosts that are deemed contact points.
    # Scylla nodes use this list of hosts to find each other and learn
    # the topology of the ring.  You must change this if you are running
    # multiple nodes!
    - class_name: org.apache.cassandra.locator.SimpleSeedProvider
          # seeds is actually a comma-delimited list of addresses.
          # Ex: "<ip1>,<ip2>,<ip3>"
          - seeds: ""

# Address or interface to bind to and tell other Scylla nodes to connect to.
# You _must_ change this if you want multiple nodes to be able to communicate!
# Setting listen_address to is always wrong.
listen_address: localhost

# Address to broadcast to other Scylla nodes
# Leaving this blank will set it to the same value as listen_address
# broadcast_address:

# port for the CQL native transport to listen for clients on
# For security reasons, you should not expose this port to the internet.  Firewall it if needed.
native_transport_port: 9042

# Uncomment to enable experimental features
# experimental: true

By default scylla.yaml is located at /etc/scylla/scylla.yaml. Note that the file will open as read-only unless you edit it as the root user or by using sudo.

scylla.yaml Required Settings

The following configuration items must be set




Name of the cluster, all the nodes in the cluster must have the same name


Seed nodes are used during startup to bootstrap the gossip process and join the cluster


IP address that the Scylla use to connect to other Scylla nodes in the cluster


IP address of the interface for client connections (Thrift, CQL)

Enabling Experimental Features

There are two ways to enable experimental features:

  • Enable all experimental features (which may be risky)

  • Enable only the features you want to try (available in Scylla Open Source from version 3.2)

Enable All Experimental Features

To enable all experimental features to add to the scylla.yaml:

experimental: true

Enable Specific Experimental Features

New in version 3.2: Scylla Open Source

To enable specific experimental features, add to the scylla.yaml the list of experimental features you want to enable, by setting the experimental_features array. The list of valid elements for this array can be obtained from scylla --help. Note that this list is version specific. Your results may be different. For example:

 - cdc
 - lwt

IPv6 Addresses

Starting with Scylla Open Source 3.2, Scylla Enterprise 2019.1.4, Manager 2.0, and Monitoring 3.0, you can use IPv6 addresses wherever an IPv4 address is used, including client-to-node and node-to-node communication, Scylla Manager to Scylla nodes (Scylla Manager Agent), and Monitoring to nodes.

For example:

- seeds: "2a05:d018:223:f00:971d:14af:6418:fe2d"
- listen_address: 2a05:d018:223:f00:971d:14af:6418:fe2d
- broadcast_rpc_address: 2a05:d018:223:f00:971d:14af:6418:fe2d

To enable IPv6 addressing, set the following paramerter in scylla.yaml:

enable_ipv6_dns_lookup: true

To read the rest of the Administration Guide (from the top).

To go to the System Configuration documentation, click here.


In Scylla, you can configure compression at rest and compression in transit. For compression in transit, you can configure compression between nodes or between the client and the node.

Client - Node Compression

Compression between the client and the node is set by the driver that the application is using to access Scylla.

For example:

Refer to the Drivers Page for more drivers.

Internode Compression

Internode compression is configured in the scylla.yaml

internode_compression controls whether traffic between nodes is compressed.

  • all - all traffic is compressed.

  • dc - traffic between different datacenters is compressed.

  • none - nothing is compressed (default).

Configuring TLS/SSL in scylla.yaml

Scylla versions 1.1 and greater support encryption between nodes and between client and node. See the Scylla Scylla TLS/SSL guide: for configuration settings.


Scylla uses the following ports:





CQL (native_transport_port)



SSL CQL (secure client to node)



Inter-node communication (RPC)



SSL inter-node communication (RPC)



JMX management






Prometheus API



node_exporter (Optionally)



Scylla client port (Thrift)



Native shard-aware transport port



Native shard-aware transport port (ssl)



For Scylla Manager ports, see Scylla Manager.


All ports above need to be open to external clients (CQL), external admin systems (JMX), and other nodes (RPC). REST API port can be kept closed for incoming external connections.

The JMX service, scylla-jmx, runs on port 7199. It is required in order to manage Scylla using nodetool and other Apache Cassandra-compatible utilities. The scylla-jmx process must be able to connect to port 10000 on localhost. The JMX service listens for incoming JMX connections on all network interfaces on the system.

Advanced networking

It is possible that a client, or another node, may need to use a different IP address to connect to a Scylla node from the address that the node is listening on. This is the case when a node is behind port forwarding. Scylla allows for setting alternate IP addresses.

Do not set any IP address to

Address Type



listen_address (required)

Address Scylla listens for connections from other nodes. See storage_port and ssl_storage_ports.

No default

rpc_address (required)

Address on which Scylla is going to expect Thrift and CQL clients connections. See rpc_port, native_transport_port and native_transport_port_ssl in the Networking parameters.

No default


Address that is broadcasted to tell other Scylla nodes to connect to. Related to listen_address above.



Address that is broadcasted to tell the clients to connect to. Related to rpc_address.


If other nodes can connect directly to listen_address, then broadcast_address does not need to be set.

If clients can connect directly to rpc_address, then broadcast_rpc_address does not need to be set.


For tips and examples on how to configure these addresses, refer to How to Properly Set Address Values in scylla.yaml

Core dumps

On RHEL and CentOS, the Automatic Bug Reporting Tool (ABRT) conflicts with Scylla coredump configuration. Remove it before installing Scylla: sudo yum remove -y abrt

Scylla places any core dumps in var/lib/scylla/coredump. They are not visible with the coredumpctl command. See the System Configuration Guide for details on core dump configuration scripts. Check with Scylla support before sharing any core dump, as they may contain sensitive data.

Schedule fstrim

Scylla sets up daily fstrim on the filesystem(s), containing your Scylla commitlog and data directory. This utility will discard, or trim, any blocks no longer in use by the filesystem.


Scylla exposes interfaces for online monitoring, as described below.

Monitoring Interfaces

Scylla Monitoring Interfaces

Monitoring Stack

Scylla Monitoring Stack


Scylla JMX is compatible with Apache Cassandra, exposing the relevant subset of MBeans.


For each JMX operation, attribute get and set, Scylla exposes a matching REST API. You can interact with the REST API using curl or using the Swagger UI available at your-ip:10000/ui


Scylla is designed for high performance before tuning, for fewer layers that interact in unpredictable ways, and to use better algorithms that do not require manual tuning. The following items are found in the manuals for other data stores but do not need to appear here.

Configuration un-contents

  • Generating tokens

  • Configuring virtual nodes

Operations un-contents

  • Tuning Bloom filters

  • Data caching

  • Configuring memtable throughput

  • Configuring compaction

  • Compression

Testing compaction and compression

  • Tuning Java resources

  • Purging gossip state on a node

Help with Scylla

Contact Support, or visit the Scylla Community page for peer support.

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