The latest consensus around the web for running Cassandra on EC2 seems to be "use new SSD instances." I've not seen any mention of the elephant in the room - using the new SSD instances significantly raises the cluster cost per TB. With Cassandra's strength being linear scalability to many terabytes of data, it strikes me as odd that everyone is recommending such a large storage cost hike almost without reservation.
Monthly cost comparison for a 100TB cluster (non-reserved instances): m1.xlarge (2x420 non-SSD): $30,000 (120 nodes) m3.xlarge (2x40 SSD): $250,000 (1250 nodes! Clearly not an option) i2.xlarge (1x800 SSD): $76,000 (125 nodes) Best case, the cost goes up 150%. How are others approaching these new instances? Have you migrated and eaten the costs, or are you staying on previous generation until prices come down?
