XFS, noatime, nodiratime MySQL 5.1.{21,22,23}, MyISAM Replication (Slave) Data size: my boss said we cannot talk about real database size, so don't ask.
Don't use SSD in Slave servers unless need. I/O bound that RAID cannot solve In most cases, you need to buy books to optimize your query statements, not buy SSD. In some cases, you need to reconstruct your architecture. Budget