Timeline Service 2.0 is automatically installed as part of the YARN installation process when deploying an HDP cluster using Ambari.
Timeline Service 2.0 uses HBase as the primary backing storage. Therefore, HBase is installed along with Timeline Service 2.0 as part of the YARN installation process. This is different from the HBase service that you install using Ambari.
The HBase component associated with Timeline Service 2.0 is installed either in embedded mode or as a separate system service depending on the cluster capacity.
When you upgrade an HDP cluster from 2.6.x to 3.0, the upgraded YARN service includes HBase installed in the embedded mode. If your cluster meets the capacity requirements for the HBase component associated with Timeline Service 2.0 to run as a separate ats-hbase service, you must enable the system service mode.