Notes and Constraints

Instance version

Currently, DCS supports Redis 3.0 (discontinued), 4.0, 5.0, and 6.0.

Redis instances cannot be upgraded, but data of an earlier instance can be migrated to a later one.

Data security

• To control access to DCS Redis 3.0 and Redis 6.0 professional edition instances, you can use security groups. Whitelists are not supported.
• To control access to DCS Redis 4.0, or Redis 5.0 and 6.0 basic edition instances, you can use whitelists. Security groups are not supported.
• DCS Redis 6.0 basic edition supports SSL encryption.

Data persistence

• Not available for single-node instances.
• Master/Standby, read/write splitting, and cluster (except single-replica cluster) instances: Data persistence is supported by default.

Read/Write splitting

• Read/Write splitting instances: Read/Write splitting is implemented on the server by default.
• Redis Cluster and master/standby instances: Read/Write splitting is implemented on the client, which requires manual configurations.
• Read/Write splitting is not supported for other instances.

Data backup

Automatic or manual data backup is supported on the console for instances other than single-node ones.

VPC and subnet

Fixed once the instance is created.

Changing Redis instance specifications or types

• You are advised to change instances during off-peak hours. Otherwise, the change may fail.
• Change the replica quantity and capacity separately.
• Only one replica can be deleted per operation.
• For more information, see Modifying Specifications.

Adjusting DCS instance bandwidth

• This function is unavailable for professional edition DCS Redis instances.
• This function is available only for instances in the Running state.
• The bandwidth adjustment range is from the instance's assured bandwidth to its maximum bandwidth. Generally, the maximum bandwidth per shard is 2048 Mbit/s when the physical machine of the instance node has sufficient resources.

Changing cluster instances to be across AZs

Available only for single-AZ cluster instances with two or more replicas.

• To upgrade AZs for Proxy Cluster instances:
  • Service running may fluctuate during the change. Perform this operation during off-peak hours.
  • If your application cannot reconnect or handle exceptions, try restarting the application after the change.
• To upgrade AZs for Redis Cluster instances:
  • Changing AZs will not interrupt services or the master node, but will slightly affect performance. Perform this operation during off-peak hours.
  • Changing AZs interrupts connections to some replicas. Ensure your application can automatically recover from exceptions and reconnect to Redis.

Version upgrade

To migrate an instance, the target instance version must be later than the source one. Migrating a later instance to an earlier one may fail.

Online migration

• To migrate Redis instances online on the DCS console, the network between the source and target must be connected and the SYNC and PSYNC commands must be allowed on the source.
• You cannot use public networks for online migration.
• The source must be Redis 3.0 or later.
• You are advised to perform online migration during off-peak hours. Otherwise, the CPU usage of the source instance may surge and the latency may increase.

IP switch

• The IP addresses and domain names of the source and target DCS Redis instances can be switched on the console after the source instance is fully and incrementally migrated.
• Unavailable for professional edition instances.
• Unavailable for Redis Cluster instances.