An input and output (IO) scheduler dispatches a first IO request from a first IO queue during a first dispatch cycle and dispatches a second IO request from a second IO queue during a second dispatch cycle to one or more disks, where the first IO request is the last remaining IO request in the first queue and the second IO request is the first overall IO request in the second queue. The first and second IO requests are selected from multiple IO requests received from one or more clients for accessing the one or more disks. A seek time monitor measures disk seek time (IO queue switch time) incurred between the first IO request and the second IO request, and determines whether the first IO request and the second IO request belong to the same group. The disk seek time is attributed to a group associated with the first IO request and the second IO request, if the first IO request and the second IO request belong to the same group. If not, then this seek time incurred during queue switch is attributed to a common ancestor of two IO queues in the IO hierarchy.