This is a follow up question to this post, as I'm trying to get my head wrapped around all these cloud hosting services:
I had stumbled upon a blog and this:
Amazon Elastic Block Store (EBS) provides block level storage volumes for use with Amazon EC2 instances. Amazon EBS volumes are off-instance storage that persists independently from the life of an instance. Amazon Elastic Block Store provides highly available, highly reliable storage volumes that can be attached to a running Amazon EC2 instance and exposed as a device within the instance. Amazon EBS is particularly suited for applications that require a database, file system, or access to raw block level storage.
So it seems as though, one should connect an EC2 with an EBS. Now all that's left to be done is have your database software (on the EC2) read/write the database data files on the EBS.
AWS has so many products and they all sound pretty similar. Not sure how Rackspace and the other cloud servers have something similar or not.
I'm still fuzzy if multiple instances of EC2s can read/write to the same EBS. Or if each instance of EC2s have their own EBS and then there's some other mechanism (such as database software installed on EC2) to keep all EBSs in sync.
Also, the e-commerce platform would be Spree/Rails with PostGreSQL/MySQL database...in case someone has further insight...