You’re completely right, of course- in my thread of reasoning I argue that the buffered disk controller you’ve identified is a leaky abstraction layer. Battery

You’re completely right, of course- in my thread of reasoning I argue that the buffered disk controller you’ve identified is a leaky abstraction layer. Battery backup and RAID are forms of hardening that abstraction. In practice, we’ve allowed that particular layer to leak persistently because it’s ultimately cheaper to handle the leaks than to harden the abstraction.