Configuring the Security Keyspaces Replication Factors

Configure the replication factors appropriately for DSE 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
dse_security

Default Replication Factors

The default replication factor for the system_auth and dse_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. DSE uses a consistency level of LOCAL_ONE for all security keyspaces queries, except when using the cassandra role. For the cassandra role, DSE 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 DSE 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. Refer to 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.

DSE caches security data. For information about adjusting the cache interval, see Security properties.
dse_security: Required for each log in and for related DSE services. Contains DSE Analytic (Spark), DSE Client digest tokens, and other Kerberos related data. Less critical for pure database activities.

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

Never set the replication factor greater than the number of nodes in the datacenter.

Procedure

To change the replication factors (RF) of the 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 dse_security keyspace RF:

ALTER KEYSPACE dse_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 dse_security keyspace. If DataStax Enterprise or Spark security options are enabled on the cluster, you must also increase the replication factor for the dse_leases keyspace across all logical datacenters.

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