# Additional Knowledge: Pd Storage Space Thresholds


![left](./student-guide/diagram/03-33-1.png)

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PD calculates a score for each store, and then generates a schedule based on the score to make the score of each store as uniform as possible. There are two threshold flag for storage space related to the score calculation

- high-space-ratio: The default is 0.6. When the storage space usage ratio of a node is less than this value, PD scheduling ignores the remaining free space metric. It is mainly based on the actual data volume calculation score to ensure that each node uses space as balanced as possible.

- low-space-ratio: The default is 0.8. When the storage space usage ratio of a node exceeds this value, PD avoids scheduling data to the corresponding node as much as possible, mainly based on the calculation score of the remaining space size to avoid running out of disk space of the corresponding node.