From DDM to DDM Single-Active DR

Supported Source and Destination Databases

Prerequisites

• You have logged in to the DRS console.
• Your account balance is greater than or equal to $0 USD.
• For details about the supported DB types and versions, see Supported Databases.
• If a subaccount is used to create a DRS task, ensure that an agency has been added. To create an agency, see Agency Management.

Suggestions

• During the DR initialization, do not perform DDL operations on the service database. Otherwise, the task may be abnormal.
• During DR initialization, ensure that no data is written to the DR database to ensure data consistency before and after DR.

• The success of DR depends on environment and manual operations. To ensure a smooth DR, perform a DR trial before you start the DR task to help you detect and resolve problems in advance.
• It is recommended that you start your DR task during off-peak hours to minimize the impact on your services.
  • If the bandwidth is not limited, initialization of DR will increase query workload of the source database by 50 MB/s and occupy 2 to 4 vCPUs.
  • To ensure data consistency, tables without a primary key may be locked for 3s during disaster recovery.
  • The data in the DR process may be locked by other transactions for a long period of time, resulting in read timeout.
  • If DRS concurrently reads data from a database, it will use about 6 to 10 sessions. The impact of the connections on services must be considered.
  • If you read a table, especially a large table, during DR, the exclusive lock on that table may be blocked.
  • For more information about the impact of DRS on databases, see What Is the Impact of DRS on Source and Destination Databases?
• Data-Level Comparison

  To obtain accurate comparison results, start data comparison at a specified time point during off-peak hours. If it is needed, select Start at a specified time for Comparison Time. Due to slight time difference and continuous operations on data, data inconsistency may occur, reducing the reliability and validity of the comparison results.

Precautions

Before creating a DR task, read the following precautions:

Procedure

1. On the Disaster Recovery Management page, click Create Disaster Recovery Task.
2. On the Create Disaster Recovery Instance page, select a region, specify the task name, description, and the DR instance details, and click Next.
   Figure 1 DR task information
   

   Table 3 Task and recipient description

   Parameter	Description
   Region	The region where your service is running. You can change the region.
   Task Name	The task name consists of 4 to 50 characters, starts with a letter, and can contain only letters (case-insensitive), digits, hyphens (-), and underscores (_).
   Description	The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\

   Figure 2 DR instance information
   

   Table 4 DR instance settings

   Parameter	Description
   DR Type	Select Single-active. The DR type can be single-active or dual-active. If Dual-active is selected, two subtasks are created by default, a forward DR task and a backward DR task. NOTE: Only whitelisted users can use dual-active DR. To use this function, submit a service ticket. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.
   Disaster Recovery Relationship	Select Current cloud as standby. This parameter is available only when you select Single-active. By default, Current cloud as standby is selected. You can also select Current cloud as active. Current cloud as standby: The DR database is on the current cloud. Current cloud as active: The service database is on the current cloud.
   Service DB Engine	Select DDM.
   DR DB Engine	Select DDM.
   Network Type	The public network is used as an example. Available options: VPN or Direct Connect and Public network. By default, the value is Public network.
   DR DB Instance	The DDM instance you created.
   Disaster Recovery Instance Subnet	Select the subnet where the disaster recovery instance is located. You can also click View Subnet to go to the network console to view the subnet where the instance resides. By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides and ensure that there are available IP addresses. To ensure that the disaster recovery instance is successfully created, only subnets with DHCP enabled are displayed.
   Destination Database Access	Select Read-only. This parameter is available only when you select Single-active. During single-active disaster recovery, the DR database becomes read-only. To change the DR database to Read/Write, you can change the DR database (or destination database) to a service database by clicking Promote Current Cloud on the Disaster Recovery Monitoring tab. After the DR task is complete or deleted, you can query and read data to the DR database. When the external database functions as the DR database, the user with the superuser permission can set the database to read-only. If a DRS instance node is rebuilt due to a fault, to ensure data consistency during the DRS task restoration, the current cloud standby database is set to read-only before the task is restored. After the task is restored, the synchronization relationship recovers.
   Enterprise Project	If the DB instance has been associated with an enterprise project, select the target project from the Enterprise Project drop-down list. You can also go to the ProjectMan console to create a project. For details about how to create a project, see ProjectMan User Guide.
   Tags	This setting is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 10 tags. After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

3. On the Configure Source and Destination Databases page, wait until the DR instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the DR instance. After the connection tests are successful, select the check box before the agreement and click Next.
   • Select Current cloud as the standby for Disaster Recovery Relationship in 2.
     Figure 3 Service database information
     

     Table 5 Service database settings

     Parameter	Description
     Source Database Type	Select a service database type.
     Region	The region where the service DB instance is located. This parameter is selected by default.
     DB Instance Name	The name of the service DB instance.
     Database Username	The username for accessing the service database.
     Database Password	The password for the service database username.

     

     The IP address, domain name, username, and password of the service database are encrypted and stored in DRS and will be cleared after the task is deleted.

     Figure 4 DR database information
     

     Table 6 DR database settings

     Parameter	Description
     DB Instance Name	The DDM instance you selected when you create a synchronization task. The instance name cannot be changed.
     Database Username	The username for accessing the DR database.
     Database Password	The password for the database username. You can change the password if necessary. To change the password, perform the following operation after the task is created: If the task is in the Starting, Initializing, Disaster recovery in progress, or Disaster recovery failed status, in the DR Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password. The database username and password are encrypted and stored in the system, and will be cleared after the task is deleted.

     • Select Current cloud as active for Disaster Recovery Relationship in 2.
       Figure 5 Service database information
       

       Table 7 Service database settings

       Parameter	Description
       DB Instance Name	The DDM instance you selected when you create a synchronization task. The instance name cannot be changed.
       Database Username	The username for accessing the service database.
       Database Password	The password for the database username. You can change the password if necessary. To change the password, perform the following operation after the task is created: If the task is in the Starting, Initializing, Disaster recovery in progress, or Disaster recovery failed status, in the DR Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password. The database username and password are encrypted and stored in the system, and will be cleared after the task is deleted.

       Figure 6 DR database information
       

       Table 8 DR database settings

       Parameter	Description
       Database Type	Type of the DR database.
       Region	The region where the DDM instance is located.
       DB Instance Name	Name of the DR instance. NOTE: When the DB instance is used as the DR database, it is set to read-only. After the task is complete, the DB instance can be readable and writable.
       Database Username	Username for logging in to the DR database.
       Database Password	Password for the database username.

       

       The username and password of the DR databases are encrypted and stored in DRS, and will be cleared after the task is deleted.

4. On the Configure DR page, specify flow control and click Next.

   Table 9 DR settings

   Parameter

   Description

   Flow Control

   You can choose whether to control the flow. Yes You can customize the maximum DR speed. In addition, you can set the time range based on your service requirements. The traffic rate setting usually includes setting of a rate limiting time period and a traffic rate value. Flow can be controlled all day or during specific time ranges. The default value is All day. A maximum of three time ranges can be set, and they cannot overlap. The flow rate must be set based on the service scenario and cannot exceed 9,999 MB/s. Figure 7 Flow control No The DR speed is not limited and the outbound bandwidth of the source database is maximally used, which causes read consumption on the source database accordingly. For example, if the outbound bandwidth of the source database is 100 MB/s and 80% bandwidth is used, the I/O consumption on the source database is 80 MB/s. NOTE: Flow control mode takes effect only in the DR initialization phase. You can also change the flow control mode when the task is in the Configuration state. On the Basic Information tab, In the DR Information area, click Modify next to Flow Control. In the dialog box that is displayed, change the flow control mode. The flow control mode cannot be changed for a task that is in Starting state.

5. On the Check Task page, check the DR task.
   • If any check fails, review the failure cause and rectify the fault. After the fault is rectified, click Check Again.

     For details about how to handle check failures, see Checking Whether the Source Database Is Connected in Data Replication Service User Guide.

     Figure 8 Pre-check
     
   • If the check is complete and the check success rate is 100%, click Next.
     

     You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

6. On the displayed page, specify Start Time, Send Notification, SMN Topic, Synchronization Delay Threshold, RPO Synchronization Delay Threshold, RTO Synchronization Delay Threshold, Stop Abnormal Tasks After and DR instance details. Then, click Submit.
   Figure 9 Task startup settings
   

   Table 10 Task and recipient description

   Parameter	Description
   Start Time	Set Start Time to Start upon task creation or Start at a specified time based on site requirements. NOTE: Starting a DR task may slightly affect the performance of the service and DR databases. You are advised to start a DR task during off-peak hours.
   Send Notifications	SMN topic. This parameter is optional. If an exception occurs during disaster recovery, the system will send a notification to the specified recipients.
   SMN Topic	This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber. For details, see Simple Message Notification User Guide.
   Synchronization Delay Threshold	During disaster recovery, a synchronization delay indicates a time difference (in seconds) of synchronization between the service and DR database. If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes. NOTE: Before setting the delay threshold, enable Send Notification. If the delay threshold is set to 0, no notifications will be sent to the recipient.
   RTO Synchronization Delay Threshold	If the synchronization delay from the DRS instance to the DR database exceeds the threshold you specify, DRS will notify specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes. NOTE: Before setting the RTO delay threshold, enable Send Notification. If the delay threshold is set to 0, no notifications will be sent to the recipient.
   RPO Synchronization Delay Threshold	If the synchronization delay from the DRS instance to the service database exceeds the threshold you specify, DRS will notify specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes. NOTE: Before setting the delay threshold, enable Send Notification. If the delay threshold is set to 0, no notifications will be sent to the recipient. In the early stages of an incremental disaster recovery, the synchronization delay is long because a large quantity of data is awaiting synchronization. In this case, no notifications will be sent.
   Stop Abnormal Tasks After	Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14. NOTE: Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

7. After the DR task is submitted, view and manage it on the Disaster Recovery Management page.
   • You can view the task status. For more information about task status, see Task Statuses.
   • You can click in the upper-right corner to view the latest task status.