Buying a DCS Redis Instance

You can buy one or more DCS Redis instances with the required computing capabilities and storage space based on service requirements.

DCS for Redis 3.0 can no longer be purchased. This section describes how to create a DCS Redis 4.0 or later instance.
Currently, DCS for Redis 6.0 is available only in some regions, such as CN North-Beijing4 and CN South-Guangzhou.
The supported Redis versions and instance types vary across regions.

Preparing Required Resources

DCS Redis instances are deployed in Virtual Private Clouds (VPCs), and bound to specific subnets. In this way, Redis instances are isolated with virtual networks that users can manage by themselves. To use professional edition Redis, security groups are required.

Therefore, before creating a Redis instance, prepare a VPC, security group, and subnet if you do not have one yet.

Only professional edition DCS Redis instances require security groups.

**Table 1** Dependency resources of a DCS instance
Resource	Requirement	Operations
VPC and subnet	Different Redis instances can use the same or different VPCs and subnets as required. Note the following when creating a VPC and subnet: The VPC and the DCS instance must be in the same region. Retain the default settings unless otherwise specified.	For details on how to create a VPC and subnet, see Creating a VPC. If you need to create and use a new subnet in an existing VPC, see Creating a Subnet for the VPC.
Security group	Different Redis instances can use the same security group or different security groups. Note the following when creating a security group: Set Template to Custom. After a security group is created, retain the default inbound and outbound rules. To use professional edition DCS Redis 6.0, you must add the security group rules described in Table 2. You can also add other rules as required.	For details on how to create a security group, see Creating a Security Group. For details on how to add rules to a security group, see Adding a Security Group Rule.

**Table 2** Security group rules
Direction	Protocol	Port	Source
Inbound	TCP	6379	0.0.0.0/0

Buying a DCS Redis Instance

Go to the Buy DCS Instance page.
Choose a purchase mode. Quick Config and Custom are available.

In Quick Config, several common Specification Settings are available, as shown in Figure 1. If none of them meet your needs, go to the Custom tab page to customize instance types and specifications, as shown in Figure 2.

Quick Config and Custom differ only in specification selection.

Figure 1 Quick Config

Figure 2 Custom
Specify Billing Mode.
Select a region closest to your application to reduce latency and accelerate access.
Select a project. By default, each region corresponds to a project.

Configure specifications. If you choose Quick Config, select one of the common specifications by referring to Table 3. If you choose Custom, configure instance specifications by referring to Table 4.

**Table 3** Specifications (Quick Config)
Item	Description
Basic - memory/Professional - memory	Basic and Professional editions are available. Comparing Professional and Basic Editions For example, Basic - 16GB is a basic edition instance with 16 GB memory.
Version	Version of the Redis instance. For details, see Comparing Redis Versions. NOTE: The Redis version cannot be changed once the instance is created. To use a later Redis version, create another DCS Redis instance and then migrate data from the old instance to the new one.
Instance Type	Master/Standby, Redis Cluster, and Proxy Cluster instances can be quickly configured. For details, see DCS Instance Types.
CPU Architecture	x86-based CPU can be quickly configured.
Replicas	Two replicas mean that the instance has two nodes (one master and one standby).
AZ	AZs where the master node and standby node of the instance are located.

**Table 4** Specifications (Custom)
Item	Description
Cache Engine	Only Redis is available.
Edition	Basic and Professional editions are available. Comparing Professional and Basic Editions Basic and Professional are available only when 6.0 is selected. Other versions support only Basic.
Sub-edition	Performance and Storage are available for the professional edition. Sub-edition is required only when Professional is selected.
CPU Architecture	x86 and Arm are available. x86 is recommended. Arm is unavailable in some regions.
Version	Currently supported Redis versions: 4.0, 5.0, and 6.0. For details, see Comparing Redis Versions. NOTE: The Redis version cannot be changed once the instance is created. To use a later Redis version, create another DCS Redis instance and then migrate data from the old instance to the new one.
Instance Type	Single-node, master/standby, Proxy Cluster, Redis Cluster, and read/write splitting types are supported. For more information, see DCS Instance Types. Currently, professional edition Redis 6.0 supports only master/standby instances.
AZ	AZ: If Instance Type is master/standby, read/write splitting, Proxy Cluster, or Redis Cluster, AZ and Standby AZ are displayed. In this case, select AZs for the master and standby nodes of the instance. Each region consists of multiple AZs with physically isolated power supplies and networks. The master and standby nodes of a master/standby, read/write splitting, or cluster DCS instance can be deployed in different AZs. Applications can also be deployed across AZs to achieve high availability (HA) for both data and applications. NOTE: If instance nodes in an AZ are faulty, nodes in other AZs will not be affected. This is because when the master node is faulty, the standby cache node will automatically become the master node to provide services. Such deployment achieves better disaster recovery. Deploying a DCS instance across AZs slightly reduces network efficiency compared with deploying an instance within an AZ. Therefore, if a DCS instance is deployed across AZs, synchronization between master and standby cache nodes is slightly less efficient. To accelerate access, deploy your instance and your application in the same AZ. To purchase a DCS instance in the CN South-Guangzhou region, AZ 1–5 and 6–7 cannot be selected as the master and standby AZs for an instance. The reason is that AZ 1–5 are physically distant from AZ 6–7 which may cause high internal latency. That is, if one of AZs 1–5 is selected as the primary AZ, AZs 6–7 cannot be selected as the standby AZ. This restriction applies only in the CN South-Guangzhou region.
Replicas	Enter the number of replicas. Replicas are DCS instance nodes. One replica indicates only a master node. Two replicas indicate a master node and a standby node. Three replicas indicate a master node and two standby nodes. Replica quantity range varies by version and instance type. Replicas cannot be set for single-node instances.
Sharding	This parameter is available only for cluster instances, and is single-choice. The shard size and quantity cannot be specified at once. Use default: You do not need to specify the shard size and quantity. Select one of the default instance specifications. Custom shard size: Select a shard size. Then select an instance specification. Custom shard quantity: Select a shard quantity. Then select an instance specification.
Instance Specification	In the Instance Specification area, select memory as required. For more information about the instance performance, see DCS Instance Specifications. The default memory quota is displayed on the console. To increase quota, click Increase quota below the specifications. On the displayed page, fill in a quota application form and click Submit.

Configure instance network settings.
1. Select the created VPC and Subnet.
  - To access the instance in an Elastic Cloud Server (ECS), select the VPC where the ECS is.
  - The VPC and subnet are fixed once the DCS instance is created.
  - A shared VPC implements network resource sharing, and unified and efficient management and control at low O&M costs.
2. In the IPv4 Address area, set the instance (private) IP address.
  Redis Cluster and professional edition instances only support automatically-assigned IP addresses. The other instance types support both automatically-assigned IP addresses and manually-specified IP addresses. You can manually specify an IP address for your instance as required.
3. Configure Port. For basic edition Redis instances, you can specify a port numbering in the range from 1 to 65535. If no port is specified, the default port 6379 will be used.
  For Redis 6.0 professional, you cannot customize a port. The default port 6379 will be used.
4. Select the created security group from the Security Group drop-down list.
  A security group is a set of rules that control access to ECSs. It provides access policies for mutually trusted ECSs with the same security protection requirements in the same VPC.
  
  Only professional edition DCS Redis instances require security groups. Basic edition DCS Redis instances are based on VPC endpoints and do not support security groups. To control access to these instances, configure a whitelist after the instances are created.
  
  If port 6379 is not enabled for the selected security group, the Enable port 6379 check box is displayed and selected by default, indicating that after the instance is created, port 6379 will be enabled for the selected security group. If port 6379 is not enabled for the selected security group, connections to the instance may fail.
Set Instance Name.

When you create only one instance at a time, the value of Name can contain 4 to 64 characters. When you create more than one instance at a time, the value of Name can contain 4 to 56 characters. These instances are named in the format of "name-n", in which n starts from 000 and is incremented by 1. For example, if you create two instances and set Name to dcs_demo, the two instances are respectively named as dcs_demo-000 and dcs_demo-001.
Specify Enterprise Project. An enterprise project manages cloud resources by gathering relevant ones together.

If you cannot select an enterprise project, check your permissions. For details, see Why Can't I Select the Required Enterprise Project When Creating a DCS Instance?
Set the instance password.
- Select Yes or No for Password Protected.
  - Password-free access carries security risks. Exercise caution when selecting this mode.
  - After creating a password-free DCS Redis instance, you can set a password for it later by using the password reset function. For details, see Changing Password Settings for DCS Redis Instances.
- Password and Confirm Password: These parameters indicate the password of accessing the DCS Redis instance, and are displayed only when Password Protected is set to Yes.
  - For security purposes, if password-free access is disabled, the system prompts you to enter an instance-specific password when you are accessing the DCS Redis instance.
  - Keep your instance password secure and change it periodically. The system cannot detect your password.
Click Advanced Settings and set the following information as required.
1. Configure Parameter Configuration. Retain Default templates or select Use custom template as required.
  If you select Use custom template, select one from the drop-down list box. To view or modify the configuration in the selected template, click View Parameter. If no custom parameter template of the selected instance version and type is available, the selection box is empty. In this case, click View Parameter Templates to go to the template creation page to create a template. For details, see Creating a Custom Parameter Template for a DCS Instance.
2. To configure instance backup policies, enable Auto Backup.
  This parameter is displayed only when the instance type is master/standby, read/write splitting, or cluster. For details about instance backup and backup policies, see Backing Up and Restoring Instances.
3. Currently, Public Access cannot be configured during instance creation. Configure it later on the instance details page. For details, see Enabling Public Access to Redis 4.0/5.0/6.0 and Obtaining the Access Addresses.
4. Add a tag.
  Tags are used to identify cloud resources. When you have many cloud resources of the same type, you can use tags to classify cloud resources by dimension (for example, by usage, owner, or environment).
  
  If tag policies for DCS have been set in your organization, add tags to DCS instances based on these policies. If a tag does not comply with the tag policies, DCS instance creation may fail. Contact your organization administrator to learn more about tag policies.
  - If you have created predefined tags, select a predefined pair of tag key and value. Click View predefined tags. On the Tag Management Service (TMS) console, view predefined tags or create new tags.
  - You can also add a tag by entering the tag key and value. For details about how to name tags, see Managing Tags.
5. Rename critical commands.
  Currently, you can only rename the COMMAND, KEYS, FLUSHDB, FLUSHALL, HGETALL, SCAN, HSCAN, SSCAN, and ZSCAN commands. For Proxy Cluster instances, you can also rename the DBSIZE and DBSTATS commands.
6. Specify the maintenance window.
  Choose a window for DCS O&M personnel to perform maintenance on your instance. You will be contacted before any maintenance activities are performed.
7. Enter a description of the instance.
Specify Required Duration. Determine the purchase duration and whether to enable auto-renewal only when purchasing a yearly/monthly Redis instance.
Specify Quantity.
Click Next.

The displayed page shows the instance information you have specified.
Confirm the instance information and submit the request.
After the task is successfully submitted, the Cache Manager page is displayed. When the new instance is in the Running state, the instance is created successfully.