Scaling in a Cluster

Prerequisites

The target cluster is available and has no tasks in progress.

Constraints

• Only the number of nodes can be modified during cluster scale-in. The node specifications and node storage capacity cannot be modified. You can modify node specifications by referring to Changing Specifications. You can modify node storage capacity by referring to Scaling Out a Cluster.
• If you change the number and storage capacity of a specified type of node, nodes in other types will not be changed.
• Ensure that the disk usage after scale-in is less than 80% and each AZ of each node type has at least one node.
• When scaling in a cluster, the data in the node to be deleted is migrated to other nodes. The timeout threshold for data migration is five hours. If data migration is not complete within 5 hours, the cluster scale-in fails. You are advised to perform scale-in for multiple times when the cluster has huge amounts of data.
• For a cluster without master nodes, the number of remaining data nodes (including cold data nodes and other types of nodes) after scale-in must be greater than half of the original node number, and greater than the maximum number of index replicas.
• For a cluster with master nodes, the number of removed master nodes in a scale-in must be fewer than half of the original master node number. After scale-in, there has to be an odd number of master nodes, and there has to be at least three of them.
• A cluster with two nodes cannot be scaled in. You can create a cluster using a single node.
• The quota of nodes in different types varies. For details, see Table 1.

  Table 1 Number of nodes in different types

  Node Type	Number
  ess	ess: 1-32
  ess, ess-master	ess: 1-200 ess-master: an odd number ranging from 3 to 9
  ess, ess-client	ess: 1-32 ess-client: 1-32
  ess, ess-cold	ess: 1-32 ess-cold: 1-32
  ess, ess-master, ess-client	ess: 1-200 ess-master: an odd number ranging from 3 to 9 ess-client: 1-32
  ess, ess-master, ess-cold	ess: 1-200 ess-master: an odd number ranging from 3 to 9 ess-cold: 1-32
  ess, ess-client, ess-cold	ess: 1-32 ess-client: 1-32 ess-cold: 1-32
  ess, ess-master, ess-client, ess-cold	ess: 1-200 ess-master: an odd number ranging from 3 to 9 ess-client: 1-32 ess-cold: 1-32
  Details about the four node types: ess: the default node type that is mandatory for cluster creation. The other three node types are optional. ess-master: master node ess-client: client node ess-cold: cold data node

Procedure

1. Log in to the CSS management console.
2. In the navigation pane, choose a cluster type. The cluster management page is displayed.
3. Choose More > Modify Configuration in the Operation column of the target cluster. The Modify Configuration page is displayed.
4. On the Modify Configuration page, choose the Scale Cluster tab and click Scale in to set parameters.
   • Action: Select Scale in.
   • Resources: The changed amount of resources.
   • Nodes: The number of the default data nodes. For details about the value range that can be changed, see Table 1.
5. Click Next.
6. Confirm the information and click Submit.
7. Click Back to Cluster List to switch to the Clusters page. The Task Status is Scaling in. When Cluster Status changes to Available, the cluster has been successfully scaled in.