In order to maintain homeostasis. mature cells removed from the top compartment of hierarchical tissues have to be replenished by means of differentiation and self-renewal events happening in the more primitive compartments. As each cell division is associated with a risk of mutation. cell division patterns have to be optimized. https://www.roneverhart.com/Seagate-Exos-7E2-ST1000NM0008-1TB-7-2K-RPM-SATA-6Gb-s-512n-128MB-3-5-Hard-Drive/