What Are the Differences Between Online and Offline Specification Changes of GeminiDB Redis Nodes? How Long Will the Changes Take? What Are the Impacts on Services?

• Online change: Nodes are changed in rolling mode. The change duration is positively related to the number of nodes. Each node takes about 5 to 10 minutes. In addition, both primary/standby and cluster instances contain three internal management nodes, which are changed at the same time. For example, three worker nodes and three internal management nodes are created for a GeminiDB Redis instance. The online change takes about 30 to 60 minutes. While specifications are changed, the node is disconnected, and its slots become disabled and are taken over by a functional node. In addition to node disconnection , there are also other interruptions in several seconds, for example, access timeout and invisible data partitions, so a reconnection mechanism must be established. You are advised to change the node specifications during off-peak hours and keep the CPU and memory usage at a low level. This prevents exceptions such as heavy load on other nodes and process startup failures.
• Offline change: Specifications of all nodes are changed concurrently. During the change, services are interrupted for about 10 to 20 minutes. Offline change is applicable when services are stopped or no service is accessed. Exercise caution when performing this operation.

For your online production services, you are advised to perform the change online. For details, see Changing vCPUs and Memory.