Recently we took advantage of the SSD instance stores available on AWS. While these are great, they obviously get deleted when the instance dies. Obviously the performance of non Provision IOPS is not great, and would be better on the SSDs. If we wanted to move our MySQL directory over to the SSD, but keep a copy on the EBS volume so if the data directory needs to be changed in the event of an instance store failure, what is the best practice for doing that? Obviously a rsync would have table locking issues. We could run two MySQL servers on the server in a replication scenario. Only one store needs to be accessed at a time, and the data would be identical. We are running Amazon Linux.
You could simply use a master-slave configuration for MySQL, simply specify the SSD machine as master, and replicate off of it.
However, I strongly recommend using RDS unless you have a truly unique setup. RDS allows for provisioned IOPS and will take care of a lot of things you need to manually do for a mysql server.