Database Requirements

This topic describes the database requirements for CDP Private Cloud Base.

Please see the Cloudera Support Matrix for detailed information about supported databases based on the CDP and Cloudera Manager versions.

Cloudera Manager and Runtime come packaged with an embedded PostgreSQL database for use in non-production environments. The embedded PostgreSQL database is not supported in production environments. For production environments, you must configure your cluster to use dedicated external databases. You must ensure latency between Cloudera Manager server and the database is < 10 ms. You can verify the latency with a simple SQL command from your Cloudera Manager server host to the database. Start your database's command line client tool and connect to the Cloudera Manager database. Run the follwoing SQL command:

SELECT 1;

After installing a database, upgrade to the latest patch and apply appropriate updates. Available updates may be specific to the operating system on which it is installed.

Notes:

Cloudera recommends installing the databases on different hosts than the services, located in the same data center. Separating databases from services can help isolate the potential impact from failure or resource contention in one or the other. It can also simplify management in organizations that have dedicated database administrators.
Data Analytics Studio requires PostgreSQL version 9.6, while RHEL 7.6 provides PostgreSQL 9.2.
Hue Query Processor in CDP 7.1.8 requires a non-SSL enabled PostgreSQL database.
Use the appropriate UTF8 encoding for Metastore, Oozie, Hive, and Hue.
Oozie also supports UTF8MB4 character encoding out of box without any configuration change when the Oozie custom database is created with the encoding of UTF8MB4.
MySQL and MariaDB must use the MySQL utf8 encoding, not utf8mb4.
Ranger only supports the InnoDB engine for MySQL and MariaDB databases.
For MySQL 5.7, you must install the MySQL-shared-compat or MySQL-shared package. This is required for the Cloudera Manager Agent installation.
MySQL GTID-based replication is not supported.
Both the Community and Enterprise versions of MySQL are supported, as well as MySQL configured by the AWS RDS service.
Before upgrading from CDH 5 to CDH 6, check the value of the COMPATIBLE initialization parameter in the Oracle Database using the following SQL query:
```
SELECT name, value FROM v$parameter WHERE name = 'compatible'
```
The default value is 12.2.0. If the parameter has a different value, you can set it to the default as shown in the Oracle Database Upgrade Guide.
note
Before resetting the COMPATIBLE initialization parameter to its default value, make sure you consider the effects of this change can have on your system.

RDBMS High Availability Support

Various Cloudera components rely on backing RDBMS services as critical infrastructure. You may require Cloudera components to support deployment in environments where RDBMS services are made highly-available. High availability (HA) solutions for RDBMS are implementation-specific, and can create constraints or behavioral changes in Cloudera components.

This section clarifies the support state and identifies known issues and limitations for HA deployments.

Upgrading Cloudera Manager and the Cloudera Manager database

When upgrading Cloudera Manager, there may be a minimum version requirement for the database server.

Ensure that the Cloudera Manager database server is upgraded to at least this minimum requirement prior to starting the new version of Cloudera Manager for the first time.

Stop Cloudera Manager Server service.
Upgrade the Cloudera Manager RPMs.
Upgrade the Cloudera Manager database server version.
Start the Cloudera Manager.

Upgrading CDP and the CDP Services databases

When upgrading CDP to a new version, the new version of CDP may have a minimum version requirement for the database server which holds services metadata.

If the database server needs to be upgraded, follow this proces:

Stop CDP services which depend on the database server, or alternatively, stop the entire cluster.
Upgrade the database server version.
Upgrade CDP using Cloudera Manager.
Start the stopped services, or the entire cluster.
When a database server upgrade is required, it is not possible to perform a rolling upgrade of the cluster.

High Availability vs. Load Balancing

Understanding the difference between HA and load balancing is important for Cloudera components, which are designed to assume services are provided by a single RDBMS instance. Load balancing distributes operations across multiple RDBMS services in parallel, while HA focuses on service continuity. Load balanced deployments are often used as part of HA strategies to overcome demands of monitoring and failover management in an HA environment. While less easier to implement, load-balanced deployments require applications tailored to the behavior and limitations of the particular technology.

Support Statement: Cloudera components are not designed for and do not support load balanced deployments of any kind. Any HA strategy involving multiple active RDBMS services must ensure all connections are routed to a single RDBMS service at any given time, regardless of vendor or HA implementation/technology.

General High Availability Support

Cloudera supports various RDBMS options, each of which have multiple possible strategies to implement HA. Cloudera cannot reasonably test and certify on each strategy for each RDBMS. Cloudera expects HA solutions for RDBMS to be transparent to Cloudera software, and therefore are not supported and debugged by Cloudera. It is the responsibility of the customer to provision, configure, and manage the RDBMS HA deployment, so that Cloudera software behaves as it would when interfacing with a single, non-HA service. Cloudera will support and help customers troubleshoot issues when a cluster has HA enabled. While diagnosing database-related problems in Cloudera components, customers may be required to temporarily disable or bypass HA mechanisms for troubleshooting purposes. If an HA-related issue is found, it is the responsibility of the customer to engage with the database vendor so that a solution to that issue can be found.

Support Statement: Cloudera Support may require customers to temporarily bypass HA layers and connect directly to supported RDBMS back-ends to troubleshoot issues. Issues observed only when connected through HA layers are the responsibility of the customer DBA staff to resolve.

RDBMS Storage Sizing

The amount of RDBMS storage space used by CDP Private Cloud Base varies depending on the services that are installed and the operations performed. Approximately, the amount of RDBMS storage needed is between 10 MB and 100 MB per host in the CDP cluster.

You can better estimate the RDBMS storage space by deploying a test cluster with the approximate proportion of service roles that the full cluster can bear. Later, execute a sample set of operations, (including Data Recovery backup) for about 24 hours and observe the storage usage on the RDBMS. Next, extrapolate the usage to the full cluster size.

Sharing an RDBMS with other applications

The ability to share an RDBMS storage between CDP Private Cloud Base and other applications depends on many factors. Cloudera recommends that you do not share the RDBMS used by CDP Private Cloud Base with any other application.

For non-production clusters where cluster size is small, not expected to grow, and occasional glitches are tolerable, it is acceptable to share a database with other applications.

MySQL

For a production cluster, CDP Runtime services must not share a database server with other applications. For small clusters, this database can be shared by the CDP Runtime services. For large clusters (hosts > 500), each CDP Runtime service must have its own database server.

PostgreSQL

If you have a dedicated database team managing high-performance hardware, with the CDP Private Cloud Base databases stored on their own spindles (or raid array), then it can be possible to have the DB server shared with other applications. When the cluster size is very large (hosts > 1000), there might be performance issues between shared applications. Cloudera recommends that you do not share the CDP Private Cloud Base database server with other application usages.

If you do not have a dedicated database team that can analyze and tune RDBMS performance, it is recommended to follow the advice for MySQL as detailed above.

Oracle

For single-server Oracle installations, see the above description related to PostgreSQL.

If you are using a clustered system like Oracle RAC, with multiple servers, it is possible to use a shared DB service, since it is no longer a single server. The end user's DB team must monitor DB latency, scale the hardware, or tune DB parameters to ensure optimal performance.

Latency target

For end users attempting to tune a shared RDBMS, ensure that elapsed times must not exceed 40 milliseconds for the 99th percentile of SELECT statements on indexed single-row queries.