1. A system comprising: a plurality of storage entities arranged in three or more hierarchical layers of virtualized storage including a first layer of virtualized storage, a second layer of virtualized storage, and a third layer of virtualized storage, wherein the plurality of storage entities is configured to: at a first storage entity at the first layer of virtualized storage, receive a request to perform an I/O task requiring a plurality of I/O operations, wherein the request specifies one or more quality of service requirements to be satisfied in performing the I/O task; in response to the request, determine a path through the three or more hierarchical layers of virtualized storage for performing the I/O task by: selecting a second storage entity for inclusion in the path from among a plurality of storage entities at the second layer of virtualized storage in response to determining that the second storage entity can satisfy the one or more quality of service requirements specified by the request; selecting a third storage entity for inclusion in the path from among a plurality of storage entities at the third layer of virtualized storage in response to determining that the third storage entity can satisfy the one or more quality of service requirements specified by the request; and wherein the plurality of storage entities is further configured to perform the I/O task through the three or more hierarchical layers of virtualized storage using the determined path such that the first storage entity at the first layer of virtualized storage communicates with the second storage entity at the second layer of virtualized storage to perform a first one or more of the plurality of I/O operations required by the task, and the second storage entity at the second layer of virtualized storage communicates with the third storage entity at the third layer of virtualized storage to perform a second one or more of the plurality of I/O operations required by the task.