Around 2009-2010, EBS volatility was leading a lot of people to run their database on instance storage instead of EBS. (At the time I suspected that even Heroku was doing this.) That seems pretty crazy, since the other name for instance storage is "ephemeral storage". If you have replication you reduce the risk, but it's still a wild thing to do. But I understand it. Would you run Postgres on NFS? If not, then why is EBS okay?

I haven't heard of people doing this for a few years, so I think PIOPS must have really improved things. But I agree, it sure is expensive! So I'm curious if anyone is still taking the instance storage approach to get more consistent disk performance.