Interestingly, on bare metal or old-school VMs, durability of local storage was pretty good. If the rack power failed, your data was probably still there. Sure, maybe it was only 99% or 99.9%, but that’s not bad if power failures are rare.

AWS etc, in contrast, have really quite abysmal durability for local disk storage. If you want the performance and cost benefits of using local storage (as opposed to S3, EBS, etc), there are plenty of server failure scenarios where the probability that your data is still there hovers around 0%.