You can create a distributed instance by purchasing an ApsaraDB for Redis instance as the first child instance or converting an existing ApsaraDB for Redis instance to the first child instance. You can use a distributed instance in scenarios such as active geo-redundancy, disaster recovery, and data synchronization across regions.

Background information

Global Distributed Cache for Redis is an active geo-redundancy database system that is developed based on ApsaraDB for Redis. Global Distributed Cache for Redis uses synchronization channels to connect multiple child instances to form a logical distributed instance. All child instances are readable and writable. Data is synchronized in real time among the child instances in a two-way manner. Global Distributed Cache for Redis supports business scenarios in which multiple sites in different regions provide services at the same time. It helps enterprises replicate the active geo-redundancy architecture of Alibaba. For more information, see Overview.

Pricing

You are not charged for creating a distributed instance. Only child instances in the distributed instance are charged in the same pricing standard for regular ApsaraDB for Redis instances. For more information, see Billing items and pricing.

Creation methods and limits

You cannot directly create a distributed instance. You can purchase an ApsaraDB for Redis instance as the first child instance of a distributed instance, or convert an existing ApsaraDB for Redis instance to the first child instance of a distributed instance. Then, the distributed instance is automatically created. The following table describes the methods of creating a distributed instance and their limits.

Method Limit Description
Create a distributed instance by purchasing an ApsaraDB for Redis instance as the first child instance The new instance must be a performance-enhanced instance of ApsaraDB for Redis Enhanced Edition (Tair). Purchase an ApsaraDB for Redis instance as the first child instance of a distributed instance. The distributed instance is automatically created.
Create a distributed instance by converting an ApsaraDB for Redis instance to the first child instance Select an existing ApsaraDB for Redis instance to convert it to the first child instance of a distributed instance. The distributed instance is automatically created.
Notice In most cases, the existing ApsaraDB for Redis instance can be accessed during the conversion. However, if the kernel version of the instance is too early to support binlogs, the system updates the kernel version of the instance during the conversion. During the update, the instance is disconnected for up to 30s and becomes read-only for up to 60s. To minimize the impacts on your business in this case, convert the instance in off-peak hours and make sure that your database clients can reconnect to the instance after the instance is disconnected.
Note For more information about the limits on distributed instances, see Limits.

Create a distributed instance by purchasing an ApsaraDB for Redis instance as the first child instance

  1. Log on to the ApsaraDB for Redis console.
  2. In the left-side navigation pane, click Global Distributed Cache.
  3. In the upper-right corner of the page that appears, choose Create Instance > Create Distributed Instance.
  4. On the buy page, select a billing method for the new instance.
    Child instances support the following billing methods:
    • Subscription: You pay for each subscription instance when you create the instance. We recommend that you select this billing method for long-term use because it is more cost-effective than the pay-as-you-go billing method. Higher discounts are offered for longer subscription periods.
    • Pay-As-You-Go: 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.
  5. 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 Select a zone within the region. 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 Select a VPC in which you want to create the ApsaraDB for Redis instance. For more information about VPCs, see Create a VPC.
    VSwitch Select a vSwitch in the VPC. If no vSwitches are created in the VPC in the selected zone, create a vSwitch first. For more information, see Create a vSwitch.
    Edition This parameter is set to Enhanced Edition (Tair) and cannot be changed.

    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 changed. For more information, see Performance-enhanced instances.
    Version This parameter is set to Redis 5.0 and cannot be changed.
    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 changed. 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 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.
  6. Click Buy Now.
  7. On the Confirm Order page, read and select the check box for the Terms of Service and complete the payment.

Create a distributed instance by converting an ApsaraDB for Redis instance to the first child instance

  1. Log on to the ApsaraDB for Redis console.
  2. In the left-side navigation pane, click Global Distributed Cache.
  3. In the upper-right corner of the page that appears, choose Create Instance > Create From Existing Instance.
  4. Select an instance to convert it to the first child instance of the distributed instance.
    Select an existing instance
    Parameter Description
    Region Select the region where the existing instance resides.
    Edition This parameter is set to Enterprise Edition and cannot be changed.
    Version This parameter is set to Redis 5.0 and cannot be changed.
    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.

    Instance Select the instance to be converted to the first child instance of the distributed instance.
  5. Click OK.
    Note After the conversion is complete, the selected ApsaraDB for Redis instance becomes the first child instance of the distributed instance. To prevent misoperations, the ApsaraDB for Redis console no longer displays the ApsaraDB for Redis instance on the Instances page. To manage the ApsaraDB for Redis instance, click Global Distributed Cache in the left-side navigation pane to go to the Global Distributed Cache page, find the distributed instance to which the ApsaraDB for Redis instance belongs, and manage the ApsaraDB for Redis instance in the distributed instance.

What to do next

Add a child instance to a distributed instance