Instance Store volumes, also referred to as Ephemeral Storage, provide temporary block-level storage and consists of preconfigured and pre-attached block of disk storage on the same physical server as the EC2 instance
Instance storage’s amount of disk storage depends on the Instance type and larger instances provide both more and larger instance store volumes. Smaller instance types such as micro instances can only be launched with EBS volumes.
Storage optimized instances provides special purpose instance storage targeted to specific uses case for e.g. HI1 provides very fast solid-state drive (SSD) backed instance storage are capable of supporting over 120,000 random read IOPS, and are optimized for very high random I/O performance and low cost per IOPS. While, HS1 instances are optimized for very high storage density, low storage cost, and high sequential I/O performance.
Instance store volumes, unlike EBS volumes, cannot be detached or attached to another instance