AWS RDS uses EBS for storage[1]. Depending on RDS instance type, I think they use multiple raid'ed EBS volumes. EBS relies on physical disks, of course, but the

AWS RDS uses EBS for storage[1]. Depending on RDS instance type, I think they use multiple raid'ed EBS volumes. EBS relies on physical disks, of course, but they're accessed as SAN devices over the network and that means higher latency than accessing disks that are hardware-attached to the local instance. EBS has historically also had somewhat variable performance (on top of the extra network latency), but the new provisioned IOPS feature should help with that[2]. [1]: http://aws.amazon.com/message/65648/ http://aws.amazon.com/message/65648/ [2]: http://aws.amazon.com/about-aws/whats-new/2012/07/31/announcing-provisioned-iops-for-amazon-ebs/ http://aws.amazon.com/about-aws/whats-new/2012/07/31/announc...