Higher RPM 3.5” hard disk drives have a higher outer band data rate due to thecircumference of the recording track. This provides an advantage in sequential performance when comparing single hard disk drives. However, the 2.5” hard disk drives are small enough that three or four can fit into the same space as a 3.5” hard disk drive and can generate higher data transfer rates if all HDDs are transferring data at the same time. Multiple 2.5” hard disk drives also provide an advantage in I/Os per gigabyte in a transactional environment by effectively reducing the seek time by 1/3 or 1/4 the normal rate. The 7200 3.5" hard disk drive shows an advantage in cost per I/O per GB if the user makes a trade-off between performance and cost.