Home > Storage > PowerScale (Isilon) > Product Documentation > Management and Migration > Storage Tiering with Dell PowerScale SmartPools > Node pool affinity
SmartPools generally allows a file to reside in only one node pool, but a file might temporarily span several node pools in some situations. A file pool policy may dictate that a file move from one node pool to another. In that case the file will exist partially on the source node pool and partially on the destination node pool until the move is complete. If the node pool configuration is changed, a file might be split across those two new pools until the next scheduled SmartPools job runs. For example, when splitting a node pool into two node pools. Consider a situation where a node pool fills up, and data spills over to another node pool so the cluster can continue accepting writes. In that case a file might be spilled over the intended node pool and the default spillover node pool. The last circumstance under which a file might span more than one node pool is for typical restriping activities such as cross-node pool rebalances or rebuilds.