Amazon is so technical, I want to confirm that my understanding is correct.

We have a large 500 GB database. (OrientDB.)

We will have it mirrored to one another in the same Availability Zone. We believe the database size will grow rapidly.

The plan is:

• Get 4 large instances that are compatible types with Placement Groups (as well as ideally, Enhanced Networking) (2 for web, 2 for DB.)
• We use an EBS-backed instances to store our operating system. Discussion here: http://alestic.com/2012/01/ec2-ebs-boot-recommended
• We can set up ephemeral SSD instance storage as swap space. (But it is lost after even a reboot. I hear its hard to add ephemeral storage if booting from EBS, but possible.)
• For offsite backup, we will take periodic snapshots and store them on S3. Obviously we need to ensure the database is in a safe state when that snapshot happens to avoid corruption. (Any hints here, aside from shutting down the DB?)
• If the database gets too big, we need to create a EBS volume that's larger. We can use RAID to break the 1 TB limit: http://alestic.com/2009/06/ec2-ebs-raid
• Static assets on web servers will be stored on S3.

Is that correct? Or am I missing something?