Each Amazon EC2 instance, unless it's a micro or M3 instance, can access storage from disks that are physically attached to the host computer. This disk storage is referred to asinstance store.
An Amazon EC2 instance store provides temporary block-level storage for use with an Amazon EC2 instance. The size of an instance store ranges from 150 GiB to up to 48 TiB, and varies by instance type. Larger instance types have larger instance stores. For more information, see Instance Stores Available on Instance Types.
An instance store consists of one or more instance store volumes. Instance store volumes must be mounted before they can be used.
By default, instances launched from an Amazon EBS-backed instance have no mounted instance store volumes. Instances launched from an instance store-backed AMI have a mounted instance store volume for the virtual machine's root device volume, and can have other mounted instances store volumes, depending on the instance type. For more information about instance store-backed AMIs and Amazon EBS-backed AMIs, see Storage for the Root Device.
Instance store volumes are usable only from a single instance during its lifetime; they can't be detached and then attached to another instance. If you create an AMI from an instance, the data on its instance store volumes isn't preserved and isn't present on the instance store volumes for the instances that you launch from this AMI. While an instance store is dedicated to a particular instance, the disk subsystem is shared among instances on a host computer, as shown in the following figure.