This topic describes how to create a read-only ApsaraDB RDS for SQL server instance. Read-only RDS instances allow your database system to process a large number of read requests. This increases the throughput of your application. Each read-only RDS instance is a replica of the primary RDS instance. This means that each read-only RDS has the same data as the primary RDS instance. Data updates on the primary RDS instance are also synchronized to each read-only RDS instance.

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

Prerequisites

The primary RDS instance runs SQL Server 2017 EE.

Precautions

  • You can create read-only RDS instances for the primary RDS instance. However, you cannot convert existing RDS instances into read-only RDS instances.
  • When you create a read-only RDS instance, ApsaraDB RDS replicates data from the secondary RDS instance to the read-only RDS instance. This avoids interruptions to your workloads on the primary RDS instance.
  • You can create up to seven read-only RDS instances.

Create a read-only RDS instance

  1. Log on to the ApsaraDB RDS console.
  2. In the top navigation bar, select the region where the primary RDS instance resides.Select a region
  3. Find the primary RDS instance and click its ID.
  4. In the Distributed by Instance Role section of the Basic Information page, click Create Read-only Instance.Create Read-only Instance
  5. Configure the following parameters and click Next: Instance Configuration.
    Parameter Description
    Billing Method
    Storage Type
    • Standard SSD: A standard SSD is an elastic block storage device that is designed based on the distributed storage architecture. You can store data on standard SSDs to separate computing from storage.
    • Enhanced SSD: An enhanced SSD is an ultra-high performance disk that is designed by Alibaba Cloud based on the next-generation distributed block storage architecture. It integrates 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. This reduces one-way latency and delivers up to 1 million random input/output operations per second (IOPS). Supported enhanced SSDs come in the following three performance levels (PLs):
      • PL1: An enhanced SSD of PL1 is a regular enhanced SSD.
      • PL2: An enhanced SSD of PL2 delivers IOPS and throughput that are twice higher than those delivered by an enhanced SSD of PL1.
      • PL3: An enhanced SSD of PL3 delivers IOPS that is 20 times higher than the IOPS delivered by an enhanced SSD of PL1. It also delivers throughput that is 11 times higher than the throughput delivered by an enhanced SSD of PL1. Enhanced SSDs of PL3 are ideal for workloads that require high I/O performance in processing concurrent requests and stable read/write latency.

    For more information about storage types, see Storage types.

    Zone The zone where the read-only RDS instance resides. Each zone is an independent physical location within a region.
    Instance Type
    • Entry-level: belongs to the general-purpose instance family. A general-purpose instance exclusively occupies the allocated memory and I/O resources. However, it shares CPU and storage resources with the other general-purpose instances that are deployed on the same server.
    • Enterprise-level: belongs to the dedicated instance family. A dedicated instance exclusively occupies the allocated CPU, memory, storage, and I/O resources. The top configuration of the dedicated instance family is dedicated host. A dedicated host instance occupies all the CPU, memory, storage, and I/O resources on the server where it is deployed.
    Note Each instance type supports a specific number of CPU cores, memory capacity, maximum number of connections, and maximum IOPS. For more information, see Primary instance types.
    Capacity The storage capacity that the read-only RDS instance has available to store data files, system files, binary log files, and transaction files. The storage capacity increases in increments of 5 GB.
    Note The dedicated instance family supports exclusive allocations of resources. Therefore, the storage capacity of each instance type with local SSDs in this family is fixed. For more information, see Primary instance types.
    Note To ensure the I/O performance that is required for data synchronization, we recommend that the specifications (memory capacity) of the read-only RDS instance be greater than or equal to the specifications (memory capacity) of the primary RDS instance.
  6. Configure the following parameters.
    Parameter Description
    Network Type
    • Classic Network: the traditional type of network.
    • VPC: A virtual private cloud (VPC) is an isolated network that provides higher security and better performance than the classic network. If you select the VPC network type, you must also specify the VPC parameter and the vSwitch of Primary Node parameter.
    Note The read-only RDS instance must have the same network type as the Elastic Compute Service (ECS) instance to which you want to connect. If both the read-only RDS instance and the ECS instance use the VPC network type, make sure that they reside in the same VPC. Otherwise, they cannot communicate over an internal network.
    Resource Group The resource group to which the read-only RDS instance belongs.
  7. Click Next: Confirm Order, confirm the settings in the Parameters section, specify the Purchase Plan parameter, read and select Terms of Service, click Pay Now, and then complete the payment.

A few minutes are required to create the read-only RDS instance.

View a read-only RDS instance

  • To view a read-only RDS instance on the Instances page, perform the following steps:
    1. Log on to the ApsaraDB RDS console.
    2. Select the region where the read-only RDS instance resides.Select a region
    3. Find the read-only RDS instance and click its ID.Read-only instance
  • To view a read-only RDS instance on the Basic Information page of the primary RDS instance, perform the following steps:
    1. Log on to the ApsaraDB RDS console.
    2. Select the region where the primary RDS instance resides.Select a region
    3. Find the primary RDS instance and click its ID.Primary instance
    4. On the Basic Information page, move the pointer over the number of read-only RDS instances and click the ID of the read-only RDS instance that you want to view.

View a read-only RDS instance on the Cluster management page

Prerequisites

The read/write splitting feature is enabled on the Cluster management page of the primary RDS instance to which the read-only RDS instance is attached. For more information, see Enable read/write splitting.
  1. Log on to the ApsaraDB RDS console.
  2. Select the region where the primary RDS instance resides.Select a region
  3. Find the primary RDS instance and click its ID.
  4. In the left-side navigation pane, click Cluster management.
  5. Find the read-only RDS instance and click its ID.

View the latency of data replication to a read-only RDS instance

When a read-only RDS instance synchronizes data from the primary RDS instance, a latency may occur. You can navigate to the Basic Information page of a read-only RDS instance to view the latency of data replication to that instance.

Related operations

Operation Description
Create read-only instance Creates a read-only ApsaraDB RDS instance.