Large but ephemeral storage for EC2 instances. Predetermined by the EC2 instance type. Stays in the local server disk. Not automatically mounted.
- docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html (archive) notably highlights what it persists, which is basically nothing
- serverfault.com/questions/433703/how-to-use-instance-store-volumes-storage-in-amazon-ec2 mentions that you have to mount it