Thanks seldo, interesting. Just been looking at a client's Amazon dashboard where they have a small set-up running, not something I normally deal with but I see their RDS is billing over 2e9 I/Os/month and ends up being a significant part of the non-fixed bit of their bill. I suspect their MySQL queries are doing table scans and building temporary tables for some of the queries; these would both up the I/O count as all RDS storage is EBS, even temporaries?

So if your MySQL storage is ephemeral how do you cope with outage? Replicate it off AWS?