Setting security keyspaces replication factors

Prerequisite, increase replication factors (RF) for security keyspaces which manage authentication and authorization to prevent lockouts and ensure consistency across the cluster.

You must configure the replication factors appropriate for using DSE Security in production environments. The keyspaces that require an increased replication factor are:

system_auth
dse_security

Note: DSE Unified Authentication stores authentication and authorization in the security keyspaces. Read access to security_auth and dse_security keyspaces is implicitly given to every authenticated user.

Warning: In order to log in for the first time using default user cassandra, you must increase the system_auth keyspace RF. If the keyspace is not available, the cassandra account log in fails. The cassandra account uses a consistency level of QUORUM for all requests.

Security keyspaces and tables

Read access to these system tables is implicitly given to every authenticated user because the tables are used by most DSE tools:

system_auth keyspace

Contains authorization and internal authentication data.

Table 1. system_auth tables
Table	Columns	Description
resource_role_permissons_index	resource (PK), role	Stores the role and a resource that the role has a set permission.
role_permissions	role (PK), resource, permissions	Stores the role, resource (for example keyspace_name/table_name), and the permission that the role has to access the resource.
role_members	role (PK), member	Stores the roles and role members.
roles	role (PK), can_login, is_superuser, member_of, salted_hash	Stores the role name, whether the role can be used for login, whether the role is a superuser, what other roles the role may be a member of, and a bcrypt salted hash password for the role.

dse_security keyspace

Contains DSE Spark, Kerberos digest data, and role options.

Table 2. dse_security tables
Table	Columns	Description
role_options	role, options	Role options.
digest_tokens	id, password	Kerberos digest tokens when enabled.
spark_security	dc, shared_secret	Share secret for Spark.

Default replication factors

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

All analytics keyspaces are initially created with the SimpleStrategy replication strategy and a replication factor (RF) of 1. Each of these must be updated in production environments to avoid data loss. 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. Only use the cassandra role to login and create your own full access account and then drop the cassandra role.

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, see Security properties. 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, 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.
Note: DSE caches security data, to adjust cache interval see Security properties.
dse_security: Contains DSE Analytic (Spark), DSE Client digest tokens, and other Kerberos related data. Required for related DSE services, less critical for pure database activities.
DataStax recommends using a replication factor of 1 per datacenter if none of these services are present.
Note: See the corresponding set up instructions for recommended dse_security if these services are present.

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};

Note: 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};
```
Important: 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
```
Note: After changing the replication strategy, you must run nodetool repair with the --full option.