Configure the security keyspaces replication factors

Configure the replication factors appropriately for HCD security in production environments. Change the replication class to NetworkTopologyStrategy and set the replication factor (RF) between 3 to 5 for the following security keyspaces:

system_auth
hcd_security

Default replication factors

The default replication factor for the system_auth and hcd_security keyspaces is 1.

To avoid data loss, each of these must be updated in production environments. DataStax recommends changing the replication factor before enabling authentication. HCD uses a consistency level of LOCAL_ONE for all security keyspaces queries, except when using the cassandra role. For the cassandra role, HCD uses the consistency level QUORUM. Use the cassandra role only to login and create your own full access account; then drop the cassandra role.

Increase the RF before enabling HCD authentication. The default login account, cassandra, executes all requests with QUORUM and may fail with an RF of 1.

Recommended replication factors

Determine the appropriate RF based on your failure tolerance and the size of your deployment.

system_auth: Required for each log in and for every action that affects a database object. Once a user logs in, their credentials, roles, and permissions are cached for a period set in the cassandra.yaml. For more information, see Security properties, which contains LDAP, native authentication, and authorization related data. When the keyspace is unavailable, logins and actions may fail. When located on a node in another datacenter, this scenario may cause delays that also can lead to failures. The keyspace tables are relatively small.

DataStax recommends using a replication factor of 3, 4, or 5 per datacenter.

HCD caches security data. For information about adjusting the cache interval, see Security properties.

Change the replication factors for security keyspaces

Change the system_auth keyspace RF:

ALTER KEYSPACE system_auth
    WITH REPLICATION= {'class' : 'NetworkTopologyStrategy',
                       'data_center_name' : <N>,
                       'data_center_name' : <N>};

Every time you add or remove a datacenter, you must manually reconfigure the system_auth keyspace.

Change the hcd_security keyspace RF:

ALTER KEYSPACE hcd_security
    WITH REPLICATION= {'class' : 'NetworkTopologyStrategy',
                       'data_center_name' : <N>,
                       'data_center_name' : <N>};

Every time you add or remove a datacenter, you must manually reconfigure the hcd_security keyspace. If HCD security options are enabled on the cluster, you must also increase the replication factor for the hcd_leases keyspace across all logical datacenters.

Run the nodetool repair on the security keyspaces.
```
nodetool repair --full system_auth
nodetool repair --full hcd_security
```
After changing the replication strategy, you must run nodetool repair with its --full option.

Configure the security keyspaces replication factors

Default replication factors

Recommended replication factors

Change the replication factors for security keyspaces

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