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OceanStor 9000 V300R006C00 Object Storage Service (Compatible with Amazon S3 APIs) Administrator Guide 07

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Overview of Data Balancing

Overview of Data Balancing

OceanStor 9000 can automatically start data balancing tasks after the data balancing function is triggered.

Data balancing refers to the balancing of data distribution across different storage nodes in the system. Data distribution becomes out of balance due to disk or node addition, node deletion, failing disk detection, slow disk detection, or node enabling/disabling. If this happens, data distribution is re-balanced using the data migration function.

Table 13-1 lists the trigger conditions for data balancing.

Table 13-1  Data balancing trigger conditions


Trigger Condition



Adding a node

Adding a node to a node pool triggers data migration. Some data is migrated from other nodes in the node pool to the newly added node so that data is evenly distributed in the system.

Deleting a node

Before a node is deleted, the data on the node must be migrated to other nodes.

Enabling/disabling a node

After a node is disabled, services and data on the node are switched and migrated to other nodes.

When a node is enabled, an automatic data migration is performed, migrating some data from other nodes to the newly enabled node so that data is evenly distributed in the system.


Adding a disk

Adding a disk triggers data balancing. Some data is migrated from other disks to the newly added disk so that data is evenly distributed in the system.

Detecting a failing or slow disk

When a failing disk is detected, the data on the disk must be migrated to other functioning disks before the disk can be removed.

When a slow disk is detected, the data on the disk must also be migrated to other functioning disks.

Data balancing policy is enabled by default.

Multiple data balancing tasks may be triggered during operations such as node or disk addition. Therefore, you are advised to disable data balancing policy and enable it again after the operations are completed.

If the policy is disabled, no data balancing tasks are generated during node or disk addition and failing or slow disk detection. Data distribution is automatically balanced when the policy is enabled after the addition or detection is completed.

If the policy is disabled, a node will fail to be deleted or disabled. To delete or disable a node, you must enable the policy.

Updated: 2019-04-28

Document ID: EDOC1000122523

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