Amazon Elastic Block Store (EBS) is an easy to use, high performance block storage service designed for use with Amazon Elastic Compute Cloud (EC2) for both throughput and transaction intensive workloads at any scale. A broad range of workloads, such as relational and non-relational databases, enterprise applications, containerized applications, big data analytics engines, file systems, and media workflows are widely deployed on Amazon EBS.
Application needs block level storages
Instance storage is ephemeral
Need datas to persist thru shutdowns
Need to be able to backup data volumes
More dedicated I/O capacity - Provide additional dedicated capacity for Amazon EBS I/O
Better performance - Minimies contention between Amazon EBS I/O and other traffic from your instance
Dedicated bandwidth - Deliver dedicated bw to Amazon EBS with options between 425Mbps and 14k Mbps, depending on instance type selected.