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Database Transmission Service

Redis connected over public network as the source

Migrating to Redis connected over express network

This topic describes how to create a task for migrating the Redis connected over public network to Redis connected over express network on the Database Transmission Service (DTS) console.

Prerequisites

A self-managed instance for Cache for Redis has been set up in the public network environment, with the database account and password configured.

A Redis instance has been set up with access via an express network, and a database account and password have been configured.

Set the target information as needed, as detailed below:

When using VPN to perform data migration, the local network where the self-managed database is located has been connected to Volcano Engine via VPN gateway. For detailed steps, refer to Building a cloud VPC and on-premises multi-data-center network interconnection.

If data migration requires a dedicated line connection, you need to establish a dedicated line connection between a single cloud VPC and a single on-premises data center network. For more information, refer to Configuring direct connections.

The network connectivity and service availability of the source and target databases have been confirmed.

Precautions

The migration task performs full migration and incremental migration by default. In Redis data migration, when the source database lacks SYNC or PSYNC permissions, DTS supports selecting full migration only. Full migration only uses the Scan method, migrating data by traversing the entire source database to the target. The Scan method causes a high load on the source database. Perform it during off-peak hours.

When the source database is a self-managed Cache for Redis, do not restart or switch the source or target database between primary and secondary during migration, as this will cause the migration task to fail.

In full and incremental migration tasks of Stream, do not perform double-write operations on the target database instance, as this may cause the migration task to fail.

Migrating instances with SSL enabled is not supported.

To migrate data from the Alibaba Cloud Redis to Volcano Engine Cache for Redis, the Alibaba Cloud database account must have replication permissions.

If different DBs map to the same DB and the same Key exists in different DBs, it may cause unpredictable results including data inconsistency or task failure during migration.

DTS currently does not support migrating data from Alibaba Cloud's cloud-native in-memory database Tair to Volcano Engine Cache for Redis. To migrate, submit a ticket for technical support.

During migration, do not change the instance configuration. Otherwise, the migration task will fail.

When creating a data migration task via express network, the system creates several network cards by default in your selected VPC, and the network cards are mounted by default to the subnet you selected. The network card name format is dts_shuttle_********.

You can migrate cluster edition instances by shard-to-shard migration.

During data migration, if duplicate key values are encountered in the target database, DTS will not retain the conflicting data at the destination. Instead, the data from the source will overwrite the data at the destination.

This feature is currently in beta testing. To use it, submit a ticket.

In full migration only scenarios, export (dump) timeout failures may occur if there are large keys on the source end or if the network environment is poor. It is recommended to split or delete large keys and then retry. If the task does not recover for a long time, submit a ticket to contact technical support.

When migrating to a VPC cluster edition instance, the cluster edition instance must support the Cluster Nodes command. Otherwise, the task can not be created successfully.

When the instance connected to the destination is a VPC cluster edition instance, you need to pay attention to the following information:

Each shard in a VPC Cache for Redis cluster edition instance should belong to the same VPC and subnet.

The VPC Cache for Redis cluster edition instance does not support configuration changes or switching to the primary.

The shard Bind IP of the VPC Cache for Redis cluster edition instance must be an internal IP, not a local IP (e.g., 127.0.0.1).

All shards in the VPC Cache for Redis cluster edition instance must use the same data account password.

Limits

Type	Description
Source and target database limits	Bandwidth requirements: Adequate egress bandwidth is required on the source database server. Failure to meet this prerequisite will lead to suboptimal migration performance. When certain keys in the source database use an expiration (expire) policy, a situation may arise where expired keys are not deleted promptly. This can result in the target database appearing to have fewer keys than the source database. During migration, if scaling operations occur, such as adding or removing shards, or specification changes, such as memory expansion, you need to reconfigure the task. To ensure consistent data, it is recommended to clear data that has been migrated to the target Cache for Redis instance before reconfiguring the task. During migration, if the source database connection address changes and causes the task to fail, you need to reconfigure the task. If it fails, you can submit a ticket for technical support. If it is not processed for a long time, the source database will reset the AOF file. Self-managed Cache for Redis supports the open-source PSync protocol. The account used for data migration must have the following permissions: The source database can execute sync, psync, and config get commands. The target database can execute write commands.
Other limits	It is recommended that the source and target Cache for Redis databases be the same version, or migrate from a lower version to a higher one to ensure compatibility. If you migrate from a higher version to a lower version, there may be database compatibility or data loss issues. During incremental data migration, DTS cannot confirm the execution success of Lua scripts called via EVAL or EVALSHA, as the target database does not explicitly return execution results for scripts. During full data migration, DTS consumes certain read/write resources on both the source and target databases, which may lead to an increased load on the database servers. When the database workload is heavy or server specifications are low, it may increase database pressure, even causing the database service to become unavailable and the data migration task to fail. It is recommended to perform data migration during off-peak hours. You can also increase the parameter value of the source database's client-output-buffer-limit to prevent buffer overflow when migrating large Keys. The storage space of the target Cache for Redis database must be greater than the storage space occupied by the source Cache for Redis database. When DTS transfers data using the psync and sync commands, it overwrites data in the target database. If the target database already contains the same Key, it will first execute the del operation. In the event of a transient connection failure on the source or target instance, a full data re-migration may be triggered, potentially leading to data inconsistency. If the target database's data eviction policy parameter maxmemory-policy is configured to a value other than noeviction, it may cause the target database's data to be inconsistent with the source database.

On the Create migration task page, locate the Configure source and target database wizard, and configure the following parameters.

Type	Parameter	Description
None	Task name	Optional. Customize the task name. Naming rules are as follows: Must start with a Chinese character or letter. Must be 64 characters or less. It can contain only Chinese characters, letters, digits, underscores (_), and hyphens (-).
None		Link specification	Select the link specification for the migration task. Compact, Medium and Standard are supported. tip The link specification can not be modified after the task is successfully created. For details on the link specifications, refer to Product specifications.
Source database configuration	Select an existing data source	You can choose whether to use an existing instance as needed: Use existing instances: Click Select an existing data source, then in the Select data source control panel, choose the target region from the Region drop-down list, and select the target data source. Supports selecting data sources by data source name and ID. For methods to create data sources, refer to Data source management. Do not use existing instances: If not using an existing instance, you need to configure the following database instance information.
		Instance type	Select Redis.
		Access method	Select Redis connected over public network. tip When migrating a Redis instance connected over public network, you need to add access permissions for the DTS CIDR blocks to the allowlist or security group policy on the source end in advance. Click View DTS CIDR blocks to view and copy the CIDR block.
		Host address	Enter the host address of the self-managed instance.
		Port	Enter the port number of the self-managed instance.
		Database account	The default account is default. tip When the version of Redis connected over public network is above 6.0, you can set the database account on a case-by-case basis.
		Database password	Enter the password corresponding to the database account of the self-managed instance. tip If a public network Redis instance enables password-free login, you do not need to enter the password for the instance's database account.
		Test connection	Click Test connection to verify the connection to the instance. If the test connection fails, modify the configuration based on the failure prompt, and then click Test connection again to verify the connection. The specific prompts are as follows: Connection authentication failed. Check the network: When this error prompt appears, confirm network connectivity. Connection authentication failed. Check the username and password: When this error prompt appears, verify your username and password. Invalid IP address: When this error prompt appears, verify the accuracy of the IP address.
Target database configuration	Select an existing data source	You can choose whether to use an existing instance as needed: Use existing instances: Click Select an existing data source, then in the Select data source control panel, choose the target region from the Region drop-down list, and select the target data source. Supports selecting data sources by data source name and ID. For methods to create data sources, refer to Data source management. Do not use existing instances: If not using an existing instance, you need to configure the following database instance information.
		Instance type	Select Redis.
		Access method	Select Redis connected over express network.
		Region	Select the region where the target instance is located.
		Architecture type	Select the instance architecture type as needed, supporting Standalone edition and Cluster edition. tip If the Redis connected over express network instance cluster has a Proxy service, the instance architecture type must be set to standalone edition.
		Host address	Enter the host address of the VPC instance. tip This parameter must be set when Architecture type is set to Standalone edition. Currently, only IPv4 addresses are supported for access. IPv6 addresses are not yet supported.
		Port	Enter the port number of the VPC instance. tip This parameter must be set when Architecture type is set to Standalone edition.
		Address	Enter the IP: port of all primary nodes with assigned slots in each shard of the Cache for Redis cluster in the private network connected via the dedicated line, separated by commas. For example: ip1:port1,ip2:port2,ip3:port3. tip This parameter must be set when Architecture type is set to Cluster edition. The IP: port of all primary nodes with assigned slots in each shard of the Cache for Redis cluster must be entered in this parameter.
		Virtual private cloud	Select the VPC where the target instance is located from the drop-down list, as shown below: Direct connect: Select any VPC under the CEN when achieving data connectivity through a dedicated line CEN. VPN connection: Select the VPC bound to the VPN gateway when achieving data connectivity through VPN.
		Subnet	Select a subnet within the VPC from the drop-down list. tip When migrating a Redis instance connected over express network, you need to add subnet CIDR block access permissions to the allowlist or security group policy on the source end in advance. Click View subnet CIDR blocks to view and copy CIDR blocks.
		Database account	The default account is default, and you can set the database account on a case-by-case basis.
		Database password	Enter the password corresponding to the database account of the source instance. tip When your Architecture type is set to Cluster edition, the database passwords of multiple shards must be consistent. Otherwise, the connection will fail. If the Redis instance connected over express network enables passwordless login, you do not need to enter the password for the instance database account.
		Test connection	Click Test connection to verify the connection to the instance. If the test connection fails, modify the configuration based on the failure prompt, and then click Test connection again to verify the connection. The details are as follows: Connection authentication failed. Check the network: When this error prompt appears, confirm network connectivity. Connection authentication failed. Check the username and password: When this error prompt appears, verify your username and password. Connection authentication failed, unable to create connection normally, contact customer service: When this error prompt appears, submit a ticket to contact technical staff. Invalid IP address: When this error prompt appears, verify the accuracy of the IP address. The Express network requires the subnet to have * available IPs. The current number of available IPs in the subnet is insufficient, and the task can not be created. Check the subnet resources in the VPC: When this error prompt appears, adjust the number of available IPs in the VPC subnet to ensure enough IPs in the target VPC subnet. The entered address is not a complete primary node address: When this error occurs, you need to check whether the host addresses and ports added for the connected cluster edition instance are the IPs and ports of all primary nodes in the cluster.
None	Project	Optional. Select the affiliated project for the task from the drop-down list. By default, it is under default (default project). You can also click Create new project to create a new project. For more information, refer to Creating a new project. tip To grant sub-user privileges to access resources in a specific project, refer to Modifying project privileges. After a task is created successfully, if you need to change its affiliated project, you can move the resource to another project. A project is a virtual concept that includes a set of resources, users, and roles. A project allows for a unified view and management of a set of resources, and controls the permissions of users and roles within the project for those resources.
		Tag	Optional. Click Add tag to add a tag to the instance. Tags can help you categorize cloud resources, control access to them, and allocate bills and costs. A tag is a key-value pair that identifies a cloud resource. You can use tags to categorize resources with the same characteristics from different dimensions, such as purpose or owner, making it easier to filter, aggregate, and manage your cloud resources. For more details about tags, refer to Tag overview. The rules for tag key-value pairs are as follows: Key Supports any language, characters, numbers, spaces, or symbols (_.:/=+-@). Case-sensitive, and the length is 1 to 128 characters. In UTF-8 encoded Unicode format. Keys cannot start with any form of volc:, such as Volc: or VOLC:. (Optional) Value Supports any language, character, digit, space, or symbol (_.:/=+-@). Case-sensitive, and the length is 0 to 256 characters. In UTF-8 encoded Unicode format. tip A maximum of 20 tags can be associated with a task in a single operation. A maximum of 50 tags can be associated with a single task. For a single resource, tag keys must be unique, and each tag key can have only one value.
		Billing method	Currently, only Pay-as-you-go is supported. No selection is required. tip For detailed billing information, refer to Billing instructions.

Click Next step: configure migration object.

On the Configure migration object wizard page, configure the related parameter information as shown in the table below.

tip

The migration task performs Full migration and Incremental migration by default.

If you do not need to start the migration task immediately, click Save in the lower-right corner of the page after configuring the migration object.

After saving, you will be redirected to the Migration task list page. The task status will be To be started, and you can configure the migration task at a suitable time. For configuration methods, refer to Configuring a migration task.

Parameter	Description
Migration type	Select the migration type as needed. Currently supported types are Full migration, and Incremental migration. By default, Full migration and Incremental migration are enabled, and Full migration can not be checked. If only full migration is required, you can deselect Incremental migration. If online migration is needed, select Full migration and Incremental migration simultaneously. tip In Redis data migration, when the source database lacks SYNC or PSYNC permissions, DTS supports selecting full migration only. Full migration only uses the Scan method, migrating data by traversing the entire source database to the target. The Scan method causes a high load on the source database. Perform it during off-peak hours. In full migration scenarios only, if the source end contains large keys or the network environment is poor, the dump operation may timeout and fail. It is recommended to split or delete large keys and then retry. If the task does not recover for a long time, submit a ticket to contact technical support. If only Full migration is selected and the source database keeps writing, consistency between source and target data is not guaranteed.
Migration object	In the Migration object area, check the objects to migrate. You can confirm the objects to migrate again in the Selected object area. Meanwhile, you can perform the following actions in the Selected object area: Rename databases or tables: Click the pencil icon next to the target databases to rename them. If you select entire databases in the Migration object area, you can only modify the database name in the Selected object area, and can not expand the database. Click Batch mapping to modify database names in bulk. For more information, refer to Database and table batch mapping. Filter and delete unnecessary targets: The search box in the Selected object area supports fuzzy search to batch delete unwanted databases and other targets.
Error retry time	If a migration task fails due to a disconnection between the source and target databases, the system immediately retries connecting to them multiple times within the specified time. Value range: 600 - 86400, in seconds (s). The default value is 600 seconds.

Last updated: 2026.09.02 16:10:47