Change of the Instance Type

• Supported instance type changes:
  • From single-node to master/standby: Supported by Redis 3.0 and Memcached, and not by Redis 4.0 and 5.0.
  • From master/standby to Proxy Cluster: Supported by Redis 3.0, and not by Redis 4.0 and 5.0.

    If a master/standby DCS Redis 3.0 instance has multiple databases, or if its data is not stored on DB0, the instance cannot be changed to the Proxy Cluster type. A master/standby instance can be changed to the Proxy Cluster type only if its data is stored and only stored on DB0.

  • From cluster types to other types: Not supported.
• Impact of instance type changes:
  • From single-node to master/standby:

    The instance cannot be connected for several seconds and remains read-only for about 1 minute.

  • From master/standby to Proxy Cluster:

    The instance cannot be connected and remains read-only for 5 to 30 minutes.

Scale-In and Scale-Out

• The following table lists scaling options supported by different DCS instances.

  Table 1 Scaling options supported by different DCS instances

  Cache Engine	Single-Node	Master/Standby	Cluster
  Redis 3.0	Increase and decrease	Increase and decrease	Increase
  Redis 4.0	Increase and decrease	Increase and decrease	Increase
  Redis 5.0	Increase and decrease	Increase and decrease	Increase
  Memcached	Increase and decrease	Increase and decrease	N/A

• Impact of scaling:
  • Single-node and master/standby:

    For a DCS Redis 3.0, 4.0, or 5.0 instance, connections are interrupted for several seconds and the instance remains read-only for about 1 minute.

    During scaling, only the memory of the instance is expanded. The CPU processing capability is not improved.

    Data of single-node instances may not be retained because they do not support data persistence. After the scaling, check whether the data is complete and import data if required.

  • Proxy Cluster:

    The instance can be connected, but the CPU will be occupied and the latency will increase during data migration. During scaling, new Redis Server nodes are added, and data is automatically balanced to the new nodes.

    Backup records created before scaling cannot be restored.

  • Redis Cluster:

    The instance can be connected, but the CPU usage and latency will increase during data migration. During scaling, new Redis Server nodes are added, and data is automatically balanced to the new nodes.

Procedure

1. Log in to the DCS console.
2. Click in the upper left corner of the management console and select a region and a project.
3. In the navigation pane, choose Cache Manager.
4. Choose More > Modify Specifications in the row containing the DCS instance.
5. On the Modify Specifications page, select the desired specification.
   

   If new replicas are added to a Redis Cluster instance, the Added Replicas field will be displayed on the page. Modifying the instance specification will cause the replica specification to be modified, which results in a change in price.

6. Click Next, confirm the details, and click Submit.

   You can go to Background Tasks page to view the modification status. For more information, see Viewing Background Tasks.

   Specification modification of a single-node or master/standby DCS instance takes about 5 to 30 minutes to complete, while that of a cluster DCS instance takes a longer time. After an instance is successfully modified, it changes to the Running state.

   

   • If the specification modification of a single-node DCS instance fails, the instance is temporarily unavailable for use. The specification remains unchanged. Some management operations (such as parameter configuration and specification modification) are temporarily not supported. After the specification modification is completed in the backend, the instance changes to the new specification and becomes available for use again.
   • If the specification modification of a master/standby or cluster DCS instance fails, the instance is still available for use with its original specifications. Some management operations (such as parameter configuration, backup, restoration, and specification modification) are temporarily not supported. Remember not to read or write more data than allowed by the original specifications; otherwise, data loss may occur.
   • After the specification modification is successful, the new specification of the instance takes effect.