You can create one or more read-only instances for a MyBase for SQL Server Always On instance to offload read requests from the primary instance. This improves the read performance of the database and increases the throughput of your application.

Prerequisites

A MyBase for SQL Server Always On instance is created. For more information, see Create a MyBase for SQL Server instance.

Background information

For more information about ApsaraDB for MyBase, see What is ApsaraDB for MyBase?

For more information about read-only instances, see Overview of read-only ApsaraDB RDS for SQL Server instances.

Additional considerations

  • After you update the kernel minor version of a primary instance, the kernel minor versions of all the read-only instances that are associated with the primary instance are updated. For more information, see Update the minor engine version of an ApsaraDB RDS for MySQL instance.
  • If you modify the configurations of a primary instance, all the read-only instances that are associated with the primary instance are restarted.
  • You can associate up to five read-only instances with a primary instance. If you need to associate more read-only instances with the primary instance, submit a ticket.
  • The storage capacity of each read-only instance must be greater than or equal to that of the primary instance. Before you increase the storage capacity of the primary instance to scale up your database system, increase the storage capacity of the read-only instances.
  • When a primary instance is released upon expiration, all the read-only instances that are associated with the primary instance are automatically released.

Procedure

  1. Log on to the ApsaraDB for MyBase console.
  2. In the upper-left corner of the page, select the region where you want to deploy the dedicated cluster.
  3. In the left-side navigation pane, choose Instances > SQL Server.
  4. Find the primary instance for which you want to create a read-only instance and click Details in the Actions column. You are redirected to the details page of the instance in the ApsaraDB RDS console.
  5. In the left-side navigation pane, click Basic Information. On the page that appears, find the Distributed by Instance Role section and click Add Read-only Instance next to Read-only Instance.
  6. In the panel that appears, configure the following parameters.
    Parameter Description
    Storage Type

    Select a storage type for the read-only instance.

    • An enhanced SSD (ESSD) is an ultra-high performance disk that is developed by Alibaba Cloud based on the next-generation distributed block storage architecture. An ESSD uses 25 GE and remote direct memory access (RDMA) technologies. This helps reduce the one-way latency and deliver up to one million random IOPS. ESSDs can come in different performance levels (PLs). The following options are available:
      • Enhanced SSD: An ESSD of PL1 is a standard ESSD.
      • PL2 ESSD: An ESSD of PL2 can deliver approximately twice the IOPS and throughput that are delivered by an ESSD of PL1.
      • PL3 ESSD: An ESSD of PL3 can deliver up to 20 times the IOPS that is delivered by an ESSD of PL1. An ESSD of PL3 can also deliver approximately 11 times the throughput that is delivered by an ESSD of PL1. ESSDs of PL3 are suitable for scenarios in which highly concurrent I/O requests must be processed at a low read and write latency.

    For more information about storage types, see Storage types.

    Instance Type The specifications of the read-only instance.
    Note To ensure I/O performance for data synchronization, we recommend that you select an instance type that provides at least the same memory capacity as the instance type of the primary instance.
    Storage Capacity The storage capacity of the read-only instance. Configure this parameter based on the used storage of the primary instance.
    Network Type Only VPC is supported. This is because MyBase for SQL Server 2017 Enterprise Edition Always On and MyBase for SQL Server 2019 Enterprise Edition Always On support only virtual private clouds (VPCs).
    Zone The zone in which the read-only instance is deployed. By default, the zone in which the primary instance is deployed is used. You cannot change the zone.
    VPC The VPC to which the read-only instance is connected. By default, the VPC to which the primary instance is connected is used. You cannot change the VPC.
    VSwitch Select the vSwitch to which the host on which the primary instance is deployed is connected.
    Note You can also create a vSwitch.
  7. Click OK.
    Note For information about how to view a read-only instance, see View a read-only RDS instance.