What is EBS optimized instance in AWS?
Normally not all the instances EBS optimized instance type in AWS. Only specific ec2 instance types are EBS optimized.
This will trigger another question ,how EBS disks are connecting with ec2? Through ec2 instance network cards only. So your network traffic and EBS data traffic will use same NIC card. But the volume connectivity with instance is backend Amazon will control.
So now what is EBS optimized? EBS-optimized instances enable EC2 instances to fully use the IOPS provisioned on an EBS volume.
For data transfer it will not use the same network card.EBS-optimized instances deliver dedicated throughput between Amazon EC2 and Amazon EBS, with options between 500 and 12,000 Megabits per second (Mbps) depending on the instance type used.
The dedicated throughput minimizes contention between Amazon EBS I/O and other traffic from your EC2 instance, providing the best performance for your EBS volumes
EBS optimization instance type can be selected while launching time only .
You can not modify for running instance .Need to stop and upgrade the instance type which support EBS
Instance types that support EBS optimization http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSOptimized.html#ebs-optimization-support