ApsaraDB for Redis:Add a child instance to 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 as 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.

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 icon before the instance ID.
   
4. Click Add Child Instance in the upper-right corner of the child instance list.
   
5. On the buy page, select a billing method for the new child 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. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use. You are offered lower prices for longer subscription periods.
   • Pay-as-you-go (Local Disk, Including Tair): You are billed for instances on an hourly basis. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go instance, you can release it 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.
6. Configure the parameters described in the following table for the new child instance.

   Parameter	Description
   Regions	The region in which you want to create the 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 an 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, these ECS instances can access the ApsaraDB for Redis instance only over the Internet. This does not fully unleash the ApsaraDB for Redis instance performance.
   Deployment Type	Single-zone Deployment: The master and replica nodes are deployed in the same zone. This deployment type can provide single-data center disaster recovery. Dual-zone Deployment: The master node and replica node are separately deployed in the specified primary zone and secondary zone of the same region to form a zone-disaster recovery architecture.
   Primary Zone	The zone in which you want to create the instance. Each region has multiple isolated locations known as zones. Each zone has its own independent power supply and network. All of the zones in a region provide the same level of service performance. If some ECS instances are used to access an ApsaraDB for Redis instance, the instance that is deployed in the same zone as the ECS instances can be accessed at a slightly lower latency compared with the instance that is deployed in a different zone. Note If you set the Deployment Type parameter to Dual-zone Deployment, you must also set the Secondary Zone parameter to a zone that is different from the zone specified by the Primary Zone parameter. The primary zone and secondary zone together form a master-replica zone-disaster recovery architecture.
   Network Type	VPC: A virtual private cloud (VPC) is an isolated network with higher security and better performance than the classic network. Important 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 the VPC network type is selected, 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	The VPC in which you want to create the instance. If you do not have a VPC, create one first. For more information, see Create and manage a VPC.
   vSwitch	The vSwitch that you want to connect to the instance in the VPC. If no vSwitches are created in the VPC in the selected zone, create a vSwitch first. For more information, see Create and manage a vSwitch.
   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 Performance-enhanced and cannot be changed. For more information, see DRAM-based 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 bottlenecks that is caused by the single-threading model. You can use high-performance cluster instances to process large-capacity workloads. Read/Write Splitting: ensures high availability, high performance, and high flexibility. 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	The number of shards for the instance. Note This parameter is supported only if the Architecture Type parameter is set 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	The instance specifications. Each instance type has a specific memory size, maximum number of connections, and bandwidth limit. For more information, see DRAM-based standard instances and DRAM-based cluster instances. Note Database metadata is generated when an ApsaraDB for Redis instance is created. The size of the metadata on each shard of a cluster instance ranges from 30 MB to 50 MB. The total size of the metadata in a cluster instance equals the total size of metadata on all shards.
   Set Password	Later: Specify a password after the instance is created. For more information, see Change or reset the password. Now: Specify a password for the instance immediately. The password must be 8 to 32 characters in length. The password must contain at least three of the following character types: uppercase letters, lowercase letters, digits, and specific special characters. These special characters include ! @ # $ % ^ & * ( ) _ + - =
   Instance Name	The name of the instance, which is used to identify and manage the instance.
   Quantity	The number of instances to create that have the same configurations. Set the value to 1.
   Subscription Duration	If you select the Subscription (Local Disk, Including Tair) billing method, you must specify the duration and specify whether to enable auto-renewal.
   Resource Group	The resource group in which to create the instance.

7. Click Buy Now.
8. On the Confirm Order page, read the service agreement and select I have read and agree to ApsaraDB for Redis (Redis/Memcache) Agreement of Service, and then complete the payment.