S Series Balancing service processing
The S Series Balancing service detects and repairs imbalances in storage availability across S Series Nodes in the same storage pool by comparing storage usage statistics.
If the service determines that storage usage is imbalanced across S Series Nodes in the same pool:
- The service determines whether each S Series Node in the pool is a source of objects to move or a target to move them to.
- From the S Series Node source, the service moves objects individually to the S Series Node target provided the storage managed by the target node does not have a copy of the object to be moved.
When selecting objects to move, the S Series Balancing service considers the size of the object data and any custom metadata that the object includes, and the age of the object. If an S Series Node is retiring, the balancing service excludes the node in its balancing algorithm.
At any point in time, HCP is unlikely to be in a perfectly balanced state for the following reasons:
- The S Series Balancing service is designed to stop balancing when the nodes are within a 10% difference threshold.
- Object additions and deletions to and from the system do not trigger the S Series Balancing service to run.
- When all the objects in a directory have been deleted, the empty directory remains in the namespace. Directories in the default namespace, whether empty or not, have metadata that takes up space.