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 into 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 by Alibaba Cloud based on ApsaraDB for Redis. Global Replica 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 Replica 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.

Billing

You are not charged for creating a distributed instance but are charged for the child instances in the distributed instance. Child instances and regular ApsaraDB for Redis instances are billed in the same manner. For more information, see Billable items and prices.

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 into the first child instance of a distributed instance. Then, the distributed instance is automatically created. The following table describes the methods for 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). For more information about performance-enhanced instances, see Performance-enhanced instances.
If you 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 into the first child instance
  • The instance to be converted must be a performance-enhanced instance of ApsaraDB for Redis Enhanced Edition (Tair). For more information about performance-enhanced instances, see Performance-enhanced instances.
    Note If your instance does not meet this limit, you can change the instance series and then convert the instance into the first child instance. For more information, see Change the configurations of an instance.
  • The direct connection mode must be disabled for the instance to be converted. For more information, see Release a direct connection endpoint.
If you select an existing ApsaraDB for Redis instance to convert it into 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 experiences a transient connection that lasts for up to 30s and remains read-only for up to 60s. To minimize the impacts on your business in this case, convert the instance during off-peak hours and make sure that your database clients can re-establish a connection.
Note For more information about the limits of 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, 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 (Local Disk, Including Tair): You must pay for each subscription instance when you create the instance. This billing method is more cost-effective than the pay-as-you-go billing method. We recommend that you select this billing method if your business scenario requires access to resources for long periods of time. Larger discounts are provided 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. The pay-as-you-go billing method is suitable for short-term use. If you no longer need a pay-as-you-go ApsaraDB for Redis instance, you can release the instance to reduce costs.
    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. This prevents the ApsaraDB for Redis instance from delivering its full performance.
    Zone Select the zone where you want to create your ApsaraDB for Redis instance. Each region has multiple isolated locations known as zones. The power supply and network of each zone are independent. To minimize the network latency between an ECS instance and an ApsaraDB for Redis instance that are deployed in the same zone, connect them by using the internal network.
    Note To implement zone-disaster recovery, you can deploy the ApsaraDB for Redis instance across multiple zones in the same region.
    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.
    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.
    VPC Select 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 Select 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 the single-threading model. You can use the high-performance cluster architecture 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 Type Select the instance type. Each instance type has a 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 MB 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.
      • Special characters include

        !@#$%^&*()_+-=

    Instance Name Enter a name that can help you identify the instance.
    Quantity Select the number of instances to create that have 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 to create the instance.
  6. Click Buy Now.
  7. On the Confirm Order page, read ApsaraDB for Redis Agreement of Service and select I have read and agree to ApsaraDB for Redis Agreement of Service, and then complete the payment.

Create a distributed instance by converting an ApsaraDB for Redis instance into 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, choose Create Instance > Create From Existing Instance.
  4. Select an instance to convert into 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 modified.
    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 the single-threading model. You can use the high-performance cluster architecture 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 convert into 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 accidental operations, 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 then manage the ApsaraDB for Redis instance in the distributed instance.

What to do next

Add a child instance to a distributed instance