Abstract: If all storage array vendors buy disk drives from the same small set of disk manufacturers then why is there such a big reliability gap between storage vendors? While excellent work has revealed the reality of failure rates and types, the focus has merely been on ”what” happens when components fail. There is very little to describe “why” subsystems fail and “why” some vendors produce exceedingly reliable subsystems while others fall drastically short. Please email: firstname.lastname@example.org and request a .pdf copy of the “If Disk” WP. We think you will find this has solid technology pointers you should be aware of.