After a distributed instance is created, it contains only one child instance. You must add one or more child instances to the distributed instance for it to work as expected. After these child instances are added, data is synchronized in real time among all of them in the distributed instance.

Prerequisites

A distributed instance is created. For more information, see Create a distributed instance.

Limits

  • A new child instance that is added to a distributed instance must reside in a different zone from those of the existing child instances in the distributed instance.
  • A new child instance that is added to a distributed instance must have same architecture as those of the existing child instances in the distributed instance. For example, if the existing child instances are cluster instances, the new child instance must also be a cluster instance. For more information about cluster instances, see Cluster master-replica instances.
  • The configurations of a new child instance that is added to a distributed instance must be the same as those of the existing child instances in the distributed instance.
    Warning If the child instances in a distributed instance have different configurations, performance or capacity issues may occur.
  • A distributed instance can contain up to three child instances.

Notes about child instances

When you add a child instance to a distributed instance, you are cloning the first child instance in the distributed instance. All data on the new child instance, including the accounts, passwords, and whitelist configuration, is the same as that on the first child instance.

Notice The accounts, passwords, and whitelist configuration are synchronized to the new child instance only when the child instance is being created. After the child instance is created, you can modify the accounts, passwords, and whitelist configuration on the child instance. These modifications are not synchronized to other child instances.

Procedure

  1. Log on to the ApsaraDB for Redis console.
  2. In the left-side navigation pane, click Global Distributed Cache.
  3. Find the distributed instance that you want to manage and click the Plus sign icon before the instance ID.
    Show the list of child instances
  4. Click Add Child Instance in the upper-right corner of the child instance list.
    Add Child Instance
  5. On the buy page, select a billing method for the new instance.
    Child instances support the following billing methods:
    • Subscription (Local Disk, Including Tair): You pay for each subscription instance when you create the instance. We recommend that you select this product type for long-term use because it is more cost-effective than the product type that uses the pay-as-you-go billing method. Higher discounts are offered for longer subscription periods.
    • Pay-as-you-go (Local Disk, Including Tair): You pay for only what you use. The instance is billed on an hourly basis. We recommend that you select this billing method for short-term use. You can release your pay-as-you-go instance to reduce costs when it is no longer used.
    Note You can switch the billing method from pay-as-you-go to subscription, but cannot switch it from subscription to pay-as-you-go.
  6. Configure parameters for the child instance.
    Parameter Description
    Region Select the region where you want to create your ApsaraDB for Redis instance. You cannot change the region after the instance is created. To maximize access speed, we recommend that you select a region that is close to the geographic location of your users.
    Note To enable connections over the internal network, make sure that the ApsaraDB for Redis instance is deployed in the same region as Elastic Compute Service (ECS) instances that need to access the ApsaraDB for Redis instance. Otherwise, the ECS instances can access the ApsaraDB for Redis instance only over the Internet. Connections over the Internet may degrade the service performance.
    Zone The zone in which you want to create the ApsaraDB for Redis instance. Each region has multiple isolated locations that are known as zones. Each zone has its own independent power supply and network. To minimize the network latency between an ECS instance and an ApsaraDB for Redis instance that are deployed in the same zone, connect them through the internal network.
    Note To implement zone-disaster recovery, you can deploy the ApsaraDB for Redis instance across multiple zones.
    Network Type
    • VPC: A virtual private cloud (VPC) is an isolated network with higher security and better performance than the classic network. We recommend that you select the VPC network type.
    • Classic Network: Cloud services in the classic network are not isolated. Access control to cloud services in the classic network is implemented by the security groups or whitelist policies of the services.
    Notice
    • To enable connections over the internal network, make sure that the ApsaraDB for Redis instance is connected to the same type of network as the ECS instances or ApsaraDB RDS instances that need to access the ApsaraDB for Redis instance.
    • If you select the VPC network type, make sure that the ApsaraDB for Redis instance is connected to the same VPC as the ECS instances or ApsaraDB RDS instances that need to access the ApsaraDB for Redis instance.
    • You can change the network type of ApsaraDB for Redis instances from Classic Network to VPC. However, you cannot change the network type from VPC to Classic Network.
    VPC The VPC in which you want to create the ApsaraDB for Redis instance. If you do not have a VPC, create one first. For more information, see Create and manage a VPC.
    VSwitch The vSwitch to be used by the ApsaraDB for Redis instance in the VPC. If no vSwitches are created in the VPC in the selected zone, create a vSwitch first. For more information, see Work with vSwitches.
    Edition This parameter is set to Enhanced Edition (Tair) and cannot be modified.

    ApsaraDB for Redis Enhanced Edition (Tair) is developed based on ApsaraDB for Redis Community Edition. Compared with ApsaraDB for Redis Community Edition, ApsaraDB for Redis Enhanced Edition (Tair) provides better performance, enhanced storage support, and more data structures. For more information, see Overview.

    Series This parameter is set to Enhanced Performance and cannot be modified. For more information, see Performance-enhanced instances.
    Version This parameter is set to Redis 5.0 and cannot be modified.
    Architecture Type
    • Standard: runs in a master-replica architecture, provides high-performance caching services, and ensures high data reliability.
    • Cluster: eliminates the performance bottleneck that is caused by a single-threading model. You can use the high-performance cluster instance to process large-capacity workloads.
    • Read-Write Splitting: ensures high availability and high performance, and supports multiple specifications. The read/write splitting architecture allows a large number of concurrent reads of hot data from read replicas. This reduces the loads on the master node and minimizes O&M costs.

    For more information, see Overview.

    Shards Select the number of shards for the ApsaraDB for Redis cluster instance.
    Note This parameter is supported only when you set Architecture Type to Cluster.
    Node Type This parameter is set to Master-Replica and cannot be modified. A master-replica instance provides a master node and a replica node that are deployed in hot standby mode to support data persistence.
    Instance Class Select the instance type. Each instance type has the specific memory size, maximum number of connections, and bandwidth limit. For more information, see Performance-enhanced standard instances and Performance-enhanced cluster instances.
    Note The database metadata is generated after an ApsaraDB for Redis instance is created. The size of the metadata on each shard of a cluster instance is 30 to 50 MB. The total size of the metadata for a cluster instance equals the sum of metadata on all shards of the cluster instance.
    Password Setting
    • Later: Set a password after the instance is created. For more information, see Change or reset the password.
    • Now: Enter a password for the instance.
      • The password must be 8 to 32 characters in length.
      • The password must contain at least three of the following types of characters: uppercase letters, lowercase letters, digits, and special characters.
      • The following special characters are supported:

        !@#$%^&*()_+-=
    Instance Name Enter a name for the instance to identify and manage the instance.
    Quantity Select the number of instances to create with the same configurations. Set the value to 1.
    Duration If you select the Subscription (Local Disk, Including Tair) billing method, you must specify the duration and select whether to enable auto-renewal.
    Resource Group Select the resource group in which the instance is created.
  7. Click Buy Now.
  8. On the Confirm Order page, read and select the check box for the Terms of Service and complete the payment.

Result

When the child instance is added to the distributed instance as shown in the following figure, the state of the distributed instance changes from Changing Configuration to Running. These two child instances in the distributed instance can synchronize data to each other.
Note You can also select the region where the child instance is deployed in the upper-left corner of the Instances page in the ApsaraDB for Redis console to view and manage this child instance.
Child instance added