Balance storage data after scaling out

After the Storage service is scaled out, you can decide whether to balance the data in the Storage service.

The scaling out of the NebulaGraph's Storage service is divided into two stages. In the first stage, the status of all pods is changed to Ready. In the second stage, the commands of BALANCE DATA和BALANCE LEADER are executed to balance data. These two stages decouple the scaling out process of the controller replica from the balancing data process, so that you can choose to perform the data balancing operation during low traffic period. The decoupling of the scaling out process from the balancing process can effectively reduce the impact on online services during data migration.

You can define whether to balance data automatically or not with the parameter enableAutoBalance in the configuration file of the CR instance of the cluster you created.

Prerequisites

You have created a NebulaGraph cluster. For how to create a cluster with Kubectl, see Create a cluster with Kubectl.

Steps

The following example uses a cluster named nebula to show how to set enableAutoBalance.

1. Run the following command to access the edit page of the nebula cluster.

   kubectl edit nebulaclusters.apps.nebula-graph.io nebula
   

2. Add enableAutoBalance and set its value to true under spec.storaged.

   apiVersion: apps.nebula-graph.io/v1alpha1
   kind: NebulaCluster
   metadata:
     name: nebula
   spec:
     graphd:
       image: vesoft/nebula-graphd
       logVolumeClaim:
         resources:
           requests:
             storage: 2Gi
         storageClassName: fast-disks
       replicas: 1
       resources:
         limits:
           cpu: "1"
           memory: 1Gi
         requests:
           cpu: 500m
           memory: 500Mi
       version: v2.6.2
     imagePullPolicy: IfNotPresent
     metad:
       dataVolumeClaim:
         resources:
           requests:
             storage: 2Gi
         storageClassName: fast-disks
       image: vesoft/nebula-metad
       logVolumeClaim:
         resources:
           requests:
             storage: 2Gi
         storageClassName: fast-disks
       replicas: 1
       resources:
         limits:
           cpu: "1"
           memory: 1Gi
         requests:
           cpu: 500m
           memory: 500Mi
       version: v2.6.2
     nodeSelector:
       nebula: cloud
     reference:
       name: statefulsets.apps
       version: v1
     schedulerName: default-scheduler
     storaged:
       enableAutoBalance: true   //Set its value to true which means storage data will be balanced after the Storage service is scaled out.
       dataVolumeClaim:
         resources:
           requests:
             storage: 2Gi
         storageClassName: fast-disks
       image: vesoft/nebula-storaged
       logVolumeClaim:
         resources:
           requests:
             storage: 2Gi
         storageClassName: fast-disks
       replicas: 3
       resources:
         limits:
           cpu: "1"
           memory: 1Gi
         requests:
           cpu: 500m
           memory: 500Mi
       version: v2.6.2
   ...    
   

   • When the value of enableAutoBalance is set to true, the Storage data will be automatically balanced after the Storage service is scaled out.
   • When the value of enableAutoBalance is set to false, the Storage data will not be automatically balanced after the Storage service is scaled out.
   • When the enableAutoBalance parameter is not set, the system will not automatically balance Storage data by default after the Storage service is scaled out.

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Last update: March 13, 2023