When you do not want or can't use an SSD for price or reliability concerns. 1) A high-throughput MX/message broker server that is set up and works next 10 year

When you do not want or can't use an SSD for price or reliability concerns. 1) A high-throughput MX/message broker server that is set up and works next 10 years without a need of drive replacement. 2) ZFS SLOG (or any similar scratchpas/transaction log) for 24/7 intensive writes. In both cases similarly reliable SSD (enterprise ssds) would cost more and require more frequent replacements.