Why Does the Used Storage Capacity of GaussDB(DWS) Decrease Significantly After Scale-Out?

If you do not run the VACUUM command to clear and reclaim the storage space before the scale-out, the data deleted from the data warehouse may not release the occupied disk space, causing dirty data and disk waste.

During the scale-out, the system redistributes the data because the service data volume on the original nodes is significantly larger than that on the newly added nodes. When the redistribution starts, the system automatically performs VACUUM to free up the storage space. In this way, the used storage is reduced.

You are advised to periodically clear and reclaim the storage space by running VACUUM FULL to prevent data expansion.

If the used storage space is still large after you run VACUUM FULL, analyze whether the existing cluster flavor meets service requirements. If no, scale out the cluster.