doc-exports/docs/css/umn/css_01_0153.html

Scaling in a Cluster

If a cluster can process existing data without fully using its resources, you can scale in the cluster to reduce costs. Services are not interrupted during cluster scale-in.

Prerequisites

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

Constraints

• The node specifications and storage capacity cannot be modified during scale-in.
• 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.
• 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 on the left, choose Clusters. On the displayed Clusters page, locate the target cluster and choose More > Scale Cluster in the Operation column.
3. On the Modify Configuration page, set scale-in parameters.
   • New Nodes: The number of default nodes. For details about the quota, see Table 1.
   • If a cluster has master nodes, client nodes, or cold data nodes, you can change the node number. For details about the quotas of the master, client, and cold data node, see Table 1.
4. Click Next.
5. Confirm the information and click Submit.
6. 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.

Parent topic: Scaling In/Out a Cluster