<p>Ping An Cloud RDS supports general instances, DR instances and read-only instances.</p> <p>Each general instance, remote DR instance, intra-city read-only instance and remote read-only instance have their own domain names and ports, which can be obtained in the basic information of each instance. For more information, see basic information of the instance, see <a href="http://pinganyun.com/ssr/help/database/RDS/User_Guide_RDS_MySQL.Instance_Management.View_Instance.View_Common_Instance" target="_blank">RDS MySQL</a> and <a href="http://pinganyun.com/ssr/help/database/RDS/User_Guide_RDS_PostgreSQL.Instance_Management.View_Instance.View_Common_Instance" target="_blank">RDS PostgreSQL</a>.&nbsp; Currently, intra-city DR instance are not accessible.</p> <p><img src="https://obs-cn-shanghai.yun.pingan.com/pcp-portal/20200107143442-1ea47190903d.png" style="height:22px; margin:0px; width:90px" />: The regions and availability zones in the following figure are only examples.</p> <p><img src="https://obs-cn-shanghai.yun.pingan.com/pcp-portal/20200107151951-1987f5ef9d0d.png" style="height:524px; width:793px" /></p> <ul> <li><strong>General instance</strong>&mdash;You can create a general instance in any availability zone of a region. Ping An Cloud RDS service uses a hot backup mechanism by default. The primary host and backup host share data storage. When the connection to the primary host of a general instance fails, the system automatically switches services to the backup host of the general instance to ensure normal business operation.</li> <li><strong>Intra-city DR instance</strong>&mdash;The system automatically creates an intra-city DR instance in the same region as a general instance in the maintenance time period. The version, computing specifications, storage specifications, and billing method of the intra-city DR instance are identical with the general instance. Only one intra-city DR instance exists. When the availability zone of a general instance fails, the system switches services to the intra-city DR instance to ensure normal business operation.</li> <li><strong>Remote DR instance</strong>&mdash;You can create a remote DR instance for a general region in an region different than the general instance. Only one remote DR instance can be created in each remote region. The version, computing specifications, storage specifications, and billing method of a remote DR instance are identical with its general instance. When the region of a general instance and its intra-city DR instance fails, the system switches services to the remote DR instance to ensure normal business operation.</li> </ul> <p>To share reading and writing load in a database when many reading requests exist, you can create read-only instances.</p> <ul> <li><strong>Intra-city read-only instance</strong>&mdash;After the system successfully creates an intra-city DR instance, you can create an intra-city read-only instance in the availability zone of the intra-city DR instance. Multiple intra-city read-only instances can be created. We recommend that you create no more than five intra-city read-only instances.</li> <li><strong>Remote read-only instance</strong>&mdash;After the system successfully creates an intra-city DR instance, you can create a remote read-only instance in a remote region. Only one remote read-only instance can be created in each remote region.</li> </ul> <p>&nbsp;</p>