We study the (Delta. D) and (Delta. N) problems for double-step digraphs considering the unilateral distance. which is the minimum between the distance in the digraph and the distance in its converse digraph. https://www.roneverhart.com/Western-Digital-Ultrastar-DC-HC550-WUH721816ALE6L0-0F38460-16TB-7-2K-RPM-SATA-6Gb-s-512e-ISE-3-5in-Hard-Drive/