Abstract: A method is used in balancing I/O load on data storage systems. A slice is selected from a first storage container of a storage tier. The storage tier includes a second storage container. The slice is relocated from the first storage container of the storage tier to the second storage container of the storage tier, where I/O load of the first storage container is greater than I/O load of the second storage container.

Abstract: A storage processor of a data storage system includes a data relocation task scheduler that provides system limit control on the execution of data relocation requests. The data relocation task scheduler also provides fairness and concurrency limit enforcement by scheduling relocation requests from different provisioning domains, such as storage pools, in a fair manner. For example, the data relocation task scheduler includes stackable sets of pending task queues that store incoming data relocation requests. The data relocation task scheduler applies an iteration scheme to remove data relocation requests from the pending task queues thereby providing scheduling fairness among the queues and among the different provisioning domains within the data storage system.