EBS Volumes and its types, choose which type to use when.
Depending upon the nature of work and amount of traffic handle one can choose a different type of EBS (ELastic block storage) attached to ec2 instances.
Currently there are 2 types of EBS provided by AWS -
SSD-backed Volumes - These are fast and hence, are used where more transactional activities need to be performed like read/write operations ( for databases) with small I/O size.
HDD-Backed Volumes - These are optimized for better streaming workloads where throughput is more important.